Help lists every builtin and every way to reach it

Not a second builtin: Help already rendered "every builtin with a leader path
and the key that runs it", and the ask is "every builtin and every shortcut" —
the same listing with three more rows and one more column. A new builtin would
have been a second renderer over a superset of the same rows, and the two would
drift the first time a column moved. The prefix filter is now the degenerate
case of the index rather than a separate mode: SPC h ? reads the same array
with prefix "h", and the path-less builtins fall out on their own because an
empty path starts with nothing.

The shortcut column is folded, never typed: chordName spells a chord from Key's
OWN declarations, so a new special key names itself and an unnamed
non-printable codepoint is a compile error instead of garbage; shortcuts()
walks the cmd columns of window_keys and jump_keys, look_cmd/exec_cmd with
their keys and buttons, and topbar_str. Retarget a binding in config.zig and
this re-renders.

So Look reads `enter, right-click`, Back reads `C-o`, Kill reads `topbar`, and
Theme reads nothing at all — which is the information.

Not a picker, deliberately: n/N stepping a list holding Kill, Del and Delcol
would end the session. The names are live text, so middle-click the one you
want.

Alt-n, Alt-c, the tty toggle and the cut/paste chords cannot appear — they are
inline handlers that reach no builtin, so there is no row to put them on. Make
one a struct with a cmd column beside its binding and it appears for free.

Three goldens moved, all of them the +Help buffer's contents.

1 files changed, 52 insertions, 52 deletions

diff --git a/test/snapshots/ttyhelp.golden b/test/snapshots/ttyhelp.golden
index ec3a4fd6..318f471b 100644
--- a/test/snapshots/ttyhelp.golden
+++ b/test/snapshots/ttyhelp.golden
@@ -34,60 +34,60 @@
 |  TTY /tmp/pardes-snap/ttyhelp/cwd Del
 |  $
 |  NOR /tmp/pardes-snap/ttyhelp/cwd/+Help Del
-|     1 pardes builtins - SPC then the keys,
-|     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 j i   Forward
-|    13 SPC j j   Last
-|    14 SPC j l   Jumplist
-|    15 SPC j o   Back
-|    16 SPC k     Kill
-|    17 SPC l D   WsDiagnostics
-|    18 SPC l S   WsSymbols
-|    19 SPC l a   CodeAction
-|    20 SPC l d   Diagnostics
-|    21 SPC l h   SelectRefs
-|    22 SPC l i   Lspinfo
-|    23 SPC l k   Hover
-|    24 SPC l r   Rename
-|    25 SPC l s   Symbols
-|    26 SPC l w   Lspwhy
+|     1 pardes builtins, and how to run each:
+|     2 SPC and its keys, a chord, a button, the
+|     3 topbar - or the name, executed anywhere.
+|     4
+|     5 SPC ?     Help            topbar
+|     6 SPC c d   Delcol
+|     7 SPC c n   Newcol          topbar
+|     8 SPC d     Del
+|     9 SPC f f   Find            topbar
+|    10 SPC f g   Grep            topbar
+|    11 SPC f s   Save
+|    12 SPC h t   Tutor           topbar
+|    13 SPC j i   Forward         C-i
+|    14 SPC j j   Last
+|    15 SPC j l   Jumplist
+|    16 SPC j o   Back            C-o
+|    17 SPC k     Kill            topbar
+|    18 SPC l D   WsDiagnostics
+|    19 SPC l S   WsSymbols
+|    20 SPC l a   CodeAction
+|    21 SPC l d   Diagnostics
+|    22 SPC l h   SelectRefs
+|    23 SPC l i   Lspinfo
+|    24 SPC l k   Hover
+|    25 SPC l r   Rename
+|    26 SPC l s   Symbols
 == snap leaderworks grid=100x30 cursor=7,4
 |Kill Newcol Tutor Debug NextColor Dump Find Grep Help
 |  TTY /tmp/pardes-snap/ttyhelp/cwd Del
 |  $
 |  NOR /tmp/pardes-snap/ttyhelp/cwd/+Help Del
-|     1 pardes builtins - SPC then the keys,
-|     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 j i   Forward
-|    13 SPC j j   Last
-|    14 SPC j l   Jumplist
-|    15 SPC j o   Back
-|    16 SPC k     Kill
-|    17 SPC l D   WsDiagnostics
-|    18 SPC l S   WsSymbols
-|    19 SPC l a   CodeAction
-|    20 SPC l d   Diagnostics
-|    21 SPC l h   SelectRefs
-|    22 SPC l i   Lspinfo
-|    23 SPC l k   Hover
-|    24 SPC l r   Rename
-|    25 SPC l s   Symbols
-|    26 SPC l w   Lspwhy
+|     1 pardes builtins, and how to run each:
+|     2 SPC and its keys, a chord, a button, the
+|     3 topbar - or the name, executed anywhere.
+|     4
+|     5 SPC ?     Help            topbar
+|     6 SPC c d   Delcol
+|     7 SPC c n   Newcol          topbar
+|     8 SPC d     Del
+|     9 SPC f f   Find            topbar
+|    10 SPC f g   Grep            topbar
+|    11 SPC f s   Save
+|    12 SPC h t   Tutor           topbar
+|    13 SPC j i   Forward         C-i
+|    14 SPC j j   Last
+|    15 SPC j l   Jumplist
+|    16 SPC j o   Back            C-o
+|    17 SPC k     Kill            topbar
+|    18 SPC l D   WsDiagnostics
+|    19 SPC l S   WsSymbols
+|    20 SPC l a   CodeAction
+|    21 SPC l d   Diagnostics
+|    22 SPC l h   SelectRefs
+|    23 SPC l i   Lspinfo
+|    24 SPC l k   Hover
+|    25 SPC l r   Rename
+|    26 SPC l s   Symbols