LSP seam: async execution model, helix keymap, evaluation harness

The base every language backend plugs into. Three parts:

ASYNC. The core had no request/response shape - every effect was
fire-and-forget or instantaneous. A language query is the first thing
that answers later, so: Effect .lsp -> shell worker -> Event .lsp_resp.
tty.zig uses io.concurrent + the vaxis queue, gui.zig a detached thread
+ the mutex queue it already had for ptys; web no-ops it. The worker
never touches the core (path/source/arg are snapshotted into an LspJob),
one query in flight identified by a monotonic id so a second press makes
the first answer stale, and no rows is a legal answer.

KEYMAP. Helix's, verified against its default.rs rather than recalled.
gd/gD/gy/gi/gr and ]d/[d had no conflicts. The SPC letters did, so
pardes's own builtins moved instead of helix's: Kill k->q, Del d->wc
(closing a pane is a window op, and c is helix's own close), Dump/Restore
s?->f?, Tutor ht->T. A three-exception muscle-memory map is not a map.

RESULTS ARE +SEARCH ROWS. path:LINE:COL text, absolute. That is what
look.zig resolves and n/N step, so one row from a goto jumps and several
open a buffer - helix's multi-result picker needed no picker code.

Backends supply exactly one function (lsp.query) plus a supports set and
a name; the base has none on purpose. zig build lspbench scores them on
the same corpus: feature matrix (trusting results, not the supports
flag - a claimed-but-empty kind is reported as a false claim), cold and
warm latency, peak RSS.

Two snapshot scripts moved. leader.snap encoded the old key paths.
chordcut.snap's last two steps clicked column 5, which lands on a FILE
pane, so 'key c-b' toggled nothing and the typed text was being read as
normal-mode keys - the golden recorded no TTY pane and no cat -v output
anywhere. Pointing them at an actual shell makes both steps assert what
their comments claim, and the tty paste chord is now covered for the
first time.

4 files changed, 118 insertions, 112 deletions

diff --git a/test/snapshots/chordcut.golden b/test/snapshots/chordcut.golden
index be00dc57..6f2da745 100644
--- a/test/snapshots/chordcut.golden
+++ b/test/snapshots/chordcut.golden
@@ -339,21 +339,21 @@
 |27: 0-1 d,#444444, 2-6 #626262,#080808, 7-29 d,#080808, 30-31 d,#444444, 32-59 #bdbdbd,#080808, 60-61 d,#444444, 62-89 #bdbdbd,#080808,
 |28: 0-1 d,#444444, 2-6 #626262,#080808, 7-29 d,#080808, 30-31 d,#444444, 32-59 #bdbdbd,#080808, 60-61 d,#444444, 62-89 #bdbdbd,#080808,
 |29: 0-1 d,#444444, 2-6 #626262,#080808, 7-29 d,#080808, 30-31 d,#444444, 32-59 #bdbdbd,#080808, 60-61 d,#444444, 62-89 #bdbdbd,#080808,
-== snap ttyprobe grid=90x30 cursor=9,11
+== snap ttyprobe grid=90x30 cursor=44,13
 |Kill Newcol Tutor Debug NextColor Dump Find Grep
-|  NOR /tmp/pardes-snap/chordcu  NOR /tmp/pardes-snap/chordcu  NOR /tmp/pardes-snap/chordcu
-|     1 line 1
+|  NOR /tmp/pardes-snap/chordcu  TTY /tmp/pardes-snap/chordcu  NOR /tmp/pardes-snap/chordcu
+|     1 line 1                   $ ls
 |     2  2echo B''OO g.txt       f.txt  g.txt                  f.txt  g.txt
-|     3 line 3
-|     4 line 4line
-|     5 lline 5
-|     6 canon -echo; printf '\x    f.txt
-|     7                          BOO
-|
-|
-|
-|
-|
+|     3 line 3                   $
+|     4 line 4line               $
+|     5 lline 5                  $
+|     6                          $ echo B''OO
+|                                BOO
+|                                $ stty -icanon -echo; printf
+|                                 '\x1b[?2004h\x1b[?1000h\x1b
+|                                [?1006h'; cat -v
+|                                ^[[<0;8;10M^[[<0;8;10m^[[200
+|                                ~line^[[201~
 |
 |
 |  NOR /tmp/pardes-snap/chordcu  NOR /tmp/pardes-snap/chordcu
@@ -370,23 +370,23 @@
 |
 |
 |
-== snap ttyprompt grid=90x30 cursor=9,11
+== snap ttyprompt grid=90x30 cursor=38,15
 |Kill Newcol Tutor Debug NextColor Dump Find Grep
-|  NOR /tmp/pardes-snap/chordcu  NOR /tmp/pardes-snap/chordcu  NOR /tmp/pardes-snap/chordcu
-|     1 line 1
+|  NOR /tmp/pardes-snap/chordcu  TTY /tmp/pardes-snap/chordcu  NOR /tmp/pardes-snap/chordcu
+|     1 line 1                   $ ls
 |     2  2echo B''OO g.txt       f.txt  g.txt                  f.txt  g.txt
-|     3 line 3
-|     4 line 4line
-|     5 lline 5
-|     6 canon -echo; printf '\x    f.txt
-|     7                          BOO
-|
-|
-|
-|
-|
-|
-|
+|     3 line 3                   $
+|     4 line 4line               $
+|     5 lline 5                  $
+|     6                          $ echo B''OO
+|                                BOO
+|                                $ stty -icanon -echo; printf
+|                                 '\x1b[?2004h\x1b[?1000h\x1b
+|                                [?1006h'; cat -v
+|                                ^[[<0;8;10M^[[<0;8;10m^[[200
+|                                ~line^[[201~
+|                                $
+|                                $ line
 |  NOR /tmp/pardes-snap/chordcu  NOR /tmp/pardes-snap/chordcu
 |     1 line 1
 |     2 line 2                   f.txt  g.txt
diff --git a/test/snapshots/chordcut.snap b/test/snapshots/chordcut.snap
index a412b57e..a1b65a4d 100644
--- a/test/snapshots/chordcut.snap
+++ b/test/snapshots/chordcut.snap
@@ -118,18 +118,18 @@ snapstyle clickdismiss
 # tty paste chord: a mouse-listening app gets the click forwarded (SGR,
 # body-relative) then the register between bracketed-paste markers —
 # cat -v prints the received bytes visibly
-press left 5 11
-release left 5 11
+press left 35 11
+release left 35 11
 stable 400 5000
 key c-b
 stable 600 8000
 text stty -icanon -echo; printf '\x1b[?2004h\x1b[?1000h\x1b[?1006h'; cat -v
 key enter
 stable 700 8000
-press left 10 12
-press right 10 12
-release right 10 12
-release left 10 12
+press left 40 12
+press right 40 12
+release right 40 12
+release left 40 12
 stable 700 8000
 snap ttyprobe
 # a plain prompt (mouse modes off) gets no click bytes — just the paste;
@@ -139,9 +139,9 @@ stable 600 8000
 text stty sane; printf '\x1b[?1000l\x1b[?1006l'
 key enter
 stable 600 8000
-press left 10 12
-press right 10 12
-release right 10 12
-release left 10 12
+press left 40 12
+press right 40 12
+release right 40 12
+release left 40 12
 stable 700 8000
 snap ttyprompt
diff --git a/test/snapshots/leader.golden b/test/snapshots/leader.golden
index 934573be..5215b6ae 100644
--- a/test/snapshots/leader.golden
+++ b/test/snapshots/leader.golden
@@ -39,9 +39,9 @@
 |
 |
 |
-== snap spc-h grid=100x40 cursor=7,2
+== snap spc-f grid=100x40 cursor=7,2
 |Kill Newcol Tutor Debug NextColor Dump Find Grep
-|  NOR /tmp/pardes-snap/leader/cwd/cmds.txt S SPC h  NOR /tmp/pardes-snap/leader/cwd Del
+|  NOR /tmp/pardes-snap/leader/cwd/cmds.txt S SPC f  NOR /tmp/pardes-snap/leader/cwd Del
 |     1 Help
 |                                                    cmds.txt
 |
@@ -189,20 +189,20 @@
 |     2 or execute the name anywhere
 |     3
 |     4 SPC ?     Help
-|     5 SPC c d   Delcol
-|     6 SPC c n   Newcol
-|     7 SPC d     Del
-|     8 SPC f f   Find
-|     9 SPC f g   Grep
-|    10 SPC f s   Save
-|    11 SPC h t   Tutor
-|    12 SPC k     Kill
-|    13 SPC s d   Dump
-|    14 SPC s r   Restore
-|    15 SPC t a   Ascii
-|    16 SPC t c   Colors
-|    17 SPC t d   Debug
-|    18 SPC t l   Palette
+|     5 SPC D     WsDiagnostics
+|     6 SPC S     WsSymbols
+|     7 SPC T     Tutor
+|     8 SPC a     CodeAction
+|     9 SPC c d   Delcol
+|    10 SPC c n   Newcol
+|    11 SPC d     Diagnostics
+|    12 SPC f d   Dump
+|    13 SPC f f   Find
+|    14 SPC f g   Grep
+|    15 SPC f r   Restore
+|    16 SPC f s   Save
+|    17 SPC h     SelectRefs
+|    18 SPC k     Hover
 == snap help-group grid=100x40 cursor=7,22
 |Kill Newcol Tutor Debug NextColor Dump Find Grep
 |  NOR /tmp/pardes-snap/leader/cwd/cmds.txt Save De  NOR /tmp/pardes-snap/leader/cwd Del
@@ -226,14 +226,14 @@
 |
 |
 |  NOR /tmp/pardes-snap/leader/cwd/+Help Del
-|     1 pardes builtins under SPC h
+|     1 pardes builtins under SPC f
 |     2
-|     3 SPC h t   Tutor
-|     4
-|
-|
-|
-|
+|     3 SPC f d   Dump
+|     4 SPC f f   Find
+|     5 SPC f g   Grep
+|     6 SPC f r   Restore
+|     7 SPC f s   Save
+|     8
 |
 |
 |
@@ -267,14 +267,14 @@
 |     8
 |     9
 |  NOR /tmp/pardes-snap/leader/cwd/+Help Del
-|     1 pardes builtins under SPC h
+|     1 pardes builtins under SPC f
 |     2
-|     3 SPC h t   Tutor
-|     4
-|
-|
-|
-|
+|     3 SPC f d   Dump
+|     4 SPC f f   Find
+|     5 SPC f g   Grep
+|     6 SPC f r   Restore
+|     7 SPC f s   Save
+|     8
 |
 |
 |
@@ -308,14 +308,14 @@
 |
 |
 |  NOR /tmp/pardes-snap/leader/cwd/+Help Del
-|     1 pardes builtins under SPC h
+|     1 pardes builtins under SPC f
 |     2
-|     3 SPC h t   Tutor
-|     4
-|
-|
-|
-|
+|     3 SPC f d   Dump
+|     4 SPC f f   Find
+|     5 SPC f g   Grep
+|     6 SPC f r   Restore
+|     7 SPC f s   Save
+|     8
 |
 |
 |
@@ -353,20 +353,20 @@
 |     2 or execute the name anywhere
 |     3
 |     4 SPC ?     Help
-|     5 SPC c d   Delcol
-|     6 SPC c n   Newcol
-|     7 SPC d     Del
-|     8 SPC f f   Find
-|     9 SPC f g   Grep
-|    10 SPC f s   Save
-|    11 SPC h t   Tutor
-|    12 SPC k     Kill
-|    13 SPC s d   Dump
-|    14 SPC s r   Restore
-|    15 SPC t a   Ascii
-|    16 SPC t c   Colors
-|    17 SPC t d   Debug
-|    18 SPC t l   Palette
+|     5 SPC D     WsDiagnostics
+|     6 SPC S     WsSymbols
+|     7 SPC T     Tutor
+|     8 SPC a     CodeAction
+|     9 SPC c d   Delcol
+|    10 SPC c n   Newcol
+|    11 SPC d     Diagnostics
+|    12 SPC f d   Dump
+|    13 SPC f f   Find
+|    14 SPC f g   Grep
+|    15 SPC f r   Restore
+|    16 SPC f s   Save
+|    17 SPC h     SelectRefs
+|    18 SPC k     Hover
 == snap help-toggles grid=100x40 cursor=7,22
 |Kill Newcol Tutor Debug NextColor Dump Find Grep
 |  NOR /tmp/pardes-snap/leader/cwd/cmds.txt Save De  NOR /tmp/pardes-snap/leader/cwd Del
@@ -433,13 +433,13 @@
 |  NOR /tmp/pardes-snap/leader/cwd/+Help Del
 |     1 pardes builtins under SPC w
 |     2
-|     3 SPC w h   Left
-|     4 SPC w j   Down
-|     5 SPC w k   Up
-|     6 SPC w l   Right
-|     7 SPC w t   Toggleterm
-|     8
-|
+|     3 SPC w c   Del
+|     4 SPC w h   Left
+|     5 SPC w j   Down
+|     6 SPC w k   Up
+|     7 SPC w l   Right
+|     8 SPC w t   Toggleterm
+|     9
 |
 |
 |
diff --git a/test/snapshots/leader.snap b/test/snapshots/leader.snap
index c8e13b8e..e06d5a3c 100644
--- a/test/snapshots/leader.snap
+++ b/test/snapshots/leader.snap
@@ -6,6 +6,10 @@
 # pane with no file behind it, like +Search). The paths, the Help lines and
 # the execute dispatch are all folded out of ONE enum at comptime — so
 # executing the WORD `Help` runs the same builtin the leader does.
+#
+# The single-letter slots k/r/a/h/s/S/d/D belong to helix's LSP commands, so
+# pardes's own builtins live around them: Kill on `q`, Del in the window group
+# as `w c`, Dump/Restore in the file group, Tutor on `T`.
 file cmds.txt Help
 start 40 100 cmds.txt
 wait 8000 Kill Newcol
@@ -15,10 +19,10 @@ stable 700 20000
 key space
 stable 400 5000
 snap spc
-# ... and grows as the path is typed (`h` = the docs group)
-key h
+# ... and grows as the path is typed (`f` = the file group)
+key f
 stable 400 5000
-snap spc-h
+snap spc-f
 # Esc abandons the sequence: indicator gone, nothing ran, cursor untouched
 key esc
 settle 100
@@ -27,41 +31,43 @@ snap abandoned
 # an UNMAPPED key abandons too, rather than waiting: a typo must not leave the
 # next keystroke armed at a builtin that closes panes
 key space
-key q
+key z
 stable 400 5000
 snap unmapped
 # executing the WORD `Help` (middle-click) runs the builtin — the enum IS the
 # lookup, so a name works anywhere text lives. Every builtin, with its keys.
 press middle 9 3
 release middle 9 3
-wait 10000 SPC h t
+wait 10000 SPC T
 stable 700 15000
 snap help-word
-# `SPC h ?`: only the `h` group, rewritten into the SAME +Help buffer
+# `SPC f ?`: only the `f` group, rewritten into the SAME +Help buffer
 key space
-key h
+key f
 key ?
-wait 10000 under SPC h
+wait 10000 under SPC f
 stable 700 15000
 snap help-group
-# `SPC h t`: the Tutor builtin, zero arguments. It runs from the +Help pane,
+# `SPC T`: the Tutor builtin, zero arguments. It runs from the +Help pane,
 # but that is an output pane and not a document — so the tutor lands under
 # cmds.txt, the real doc, with the listing left at the foot of the column.
 key space
-key h
-key t
+key T
 wait 10000 PARDES TUTOR
 stable 700 15000
 snap tutor
-# `SPC d`: Del is pane-scoped — it closes the tutor, focus falls back
+# `SPC w c`: Del is pane-scoped — it closes the tutor, focus falls back. It
+# sits in the window group because closing a pane IS a window operation, and
+# because `d` now belongs to the diagnostics picker.
 key space
-key d
+key w
+key c
 stable 700 15000
 snap deleted
 # `SPC ?` at the root lists everything again
 key space
 key ?
-wait 10000 SPC s r
+wait 10000 SPC f r
 stable 700 15000
 snap help-all
 # `SPC t ?`: the toggle group, seven of them now that the image renderer
@@ -73,8 +79,8 @@ key ?
 wait 10000 Petscii
 stable 700 15000
 snap help-toggles
-# `SPC w ?`: the window group, whose five builtins are the tail of the full
-# listing above and fall off the bottom of this pane there
+# `SPC w ?`: the window group — the four focus moves, the terminal hop, and
+# Del. They are the tail of the full listing above and fall off its bottom.
 key space
 key w
 key ?