Esc alternates between the last two panes; Toggleterm is gone

Esc ran Toggleterm, which hopped between the newest DOC and the newest
TERMINAL. That distinction never earned its keep. It made Esc unpredictable —
which of three panes you landed on depended on their kinds, not on where you
had been — and it could not alternate between two files at all, which is the
case you hit most. Editing two files, Esc did nothing.

The replacement already existed. Last (SPC j j) is "the pane you were in
before this one, whichever it was": it walks the jump stack for the newest
entry naming a different pane and restores its line and column. So Esc, and
Shift-Esc in tty, now run Last, and Toggleterm is deleted rather than renamed
— a third implementation of "go to the other pane" was the thing to avoid.
SPC w t goes with it; the w group is the four directional moves, and the jump
group already had SPC j j.

Held down, Esc alternates. Two files, a file and its shell, a file and a
+Search — all the same, because Last has no notion of kind to get wrong.

This depends on the swap in the same series: Last reads the stack backwards,
and until hopping stopped appending, the pane you came from could fall off it.

windownav.snap needed only its keys and prose changed — its golden did not
move at all, which is the useful evidence here: for the one scenario the old
builtin handled well, Last produces an identical focus sequence.

Coverage for what it did not handle is new: a unit test opens a second FILE by
looking its name and asserts Esc alternates between two panes of the SAME
kind, which is the case that used to be a no-op.

Docs follow: tutor.txt, docs/helix-keys.md, docs/design.typ, and the builtin
index goldens, which are now one row shorter.

75/75 snapshots, both unit suites, and the macOS ABI build all pass.

1 files changed, 26 insertions, 26 deletions

diff --git a/test/snapshots/leader.golden b/test/snapshots/leader.golden
index c33b1633..9398b158 100644
--- a/test/snapshots/leader.golden
+++ b/test/snapshots/leader.golden
@@ -1,6 +1,6 @@
 == snap spc grid=100x40 cursor=7,2
 |New Newcol Find Grep Help Tutor Dump NextColor Debug Kill
-|  /tmp/pardes-snap/leader/cwd/cmds.txt Save New Del                                              SPC
+|  /tmp/pardes-snap/leader/cwd/cmds.txt                              Save New Del
 |     1 Help
 |
 |
@@ -38,10 +38,10 @@
 |
 |
 |
-|
+|                                                                                                 SPC
 == snap spc-h grid=100x40 cursor=7,2
 |New Newcol Find Grep Help Tutor Dump NextColor Debug Kill
-|  /tmp/pardes-snap/leader/cwd/cmds.txt Save New Del                                            SPC h
+|  /tmp/pardes-snap/leader/cwd/cmds.txt                              Save New Del
 |     1 Help
 |
 |
@@ -79,10 +79,10 @@
 |
 |
 |
-|
+|                                                                                               SPC h
 == snap abandoned grid=100x40 cursor=7,2
 |New Newcol Find Grep Help Tutor Dump NextColor Debug Kill
-|  /tmp/pardes-snap/leader/cwd/cmds.txt Save New Del
+|  /tmp/pardes-snap/leader/cwd/cmds.txt                              Save New Del
 |     1 Help
 |
 |
@@ -123,7 +123,7 @@
 |
 == snap unmapped grid=100x40 cursor=7,2
 |New Newcol Find Grep Help Tutor Dump NextColor Debug Kill
-|  /tmp/pardes-snap/leader/cwd/cmds.txt Save New Del
+|  /tmp/pardes-snap/leader/cwd/cmds.txt                              Save New Del
 |     1 Help
 |
 |
@@ -164,7 +164,7 @@
 |
 == snap help-word grid=100x40 cursor=7,22
 |New Newcol Find Grep Help Tutor Dump NextColor Debug Kill
-|  /tmp/pardes-snap/leader/cwd/cmds.txt Save New Del
+|  /tmp/pardes-snap/leader/cwd/cmds.txt                              Save New Del
 |     1 Help
 |
 |
@@ -184,7 +184,7 @@
 |
 |
 |
-|  /tmp/pardes-snap/leader/cwd/+Help New Del
+|  /tmp/pardes-snap/leader/cwd/+Help                                      New Del
 |     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.
@@ -205,7 +205,7 @@
 |    18 SPC k     Kill            topbar
 == snap help-group grid=100x40 cursor=7,22
 |New Newcol Find Grep Help Tutor Dump NextColor Debug Kill
-|  /tmp/pardes-snap/leader/cwd/cmds.txt Save New Del
+|  /tmp/pardes-snap/leader/cwd/cmds.txt                              Save New Del
 |     1 Help
 |
 |
@@ -225,7 +225,7 @@
 |
 |
 |
-|  /tmp/pardes-snap/leader/cwd/+Help New Del
+|  /tmp/pardes-snap/leader/cwd/+Help                                      New Del
 |     1 pardes builtins under SPC h
 |     2
 |     3 SPC h t   Tutor           topbar
@@ -246,7 +246,7 @@
 |
 == snap tutor grid=100x40 cursor=7,12
 |New Newcol Find Grep Help Tutor Dump NextColor Debug Kill
-|  /tmp/pardes-snap/leader/cwd/cmds.txt Save New Del
+|  /tmp/pardes-snap/leader/cwd/cmds.txt                              Save New Del
 |     1 Help
 |
 |
@@ -256,7 +256,7 @@
 |
 |
 |
-|  /Tutor Save New Del
+|  /Tutor                                                            Save New Del
 |     1
 |     2                                PARDES TUTOR
 |     3                      tmux + vi + acme, from scratch.
@@ -266,7 +266,7 @@
 |     7         Press j until you reach the introduction.
 |     8
 |     9
-|  /tmp/pardes-snap/leader/cwd/+Help New Del
+|  /tmp/pardes-snap/leader/cwd/+Help                                      New Del
 |     1 pardes builtins under SPC h
 |     2
 |     3 SPC h t   Tutor           topbar
@@ -287,7 +287,7 @@
 |
 == snap deleted grid=100x40 cursor=7,22
 |New Newcol Find Grep Help Tutor Dump NextColor Debug Kill
-|  /tmp/pardes-snap/leader/cwd/cmds.txt Save New Del
+|  /tmp/pardes-snap/leader/cwd/cmds.txt                              Save New Del
 |     1 Help
 |
 |
@@ -307,7 +307,7 @@
 |
 |
 |
-|  /tmp/pardes-snap/leader/cwd/+Help New Del
+|  /tmp/pardes-snap/leader/cwd/+Help                                      New Del
 |     1 pardes builtins under SPC h
 |     2
 |     3 SPC h t   Tutor           topbar
@@ -328,7 +328,7 @@
 |
 == snap help-all grid=100x40 cursor=7,22
 |New Newcol Find Grep Help Tutor Dump NextColor Debug Kill
-|  /tmp/pardes-snap/leader/cwd/cmds.txt Save New Del
+|  /tmp/pardes-snap/leader/cwd/cmds.txt                              Save New Del
 |     1 Help
 |
 |
@@ -348,7 +348,7 @@
 |
 |
 |
-|  /tmp/pardes-snap/leader/cwd/+Help New Del
+|  /tmp/pardes-snap/leader/cwd/+Help                                      New Del
 |     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.
@@ -369,7 +369,7 @@
 |    18 SPC k     Kill            topbar
 == snap help-toggles grid=100x40 cursor=7,22
 |New Newcol Find Grep Help Tutor Dump NextColor Debug Kill
-|  /tmp/pardes-snap/leader/cwd/cmds.txt Save New Del
+|  /tmp/pardes-snap/leader/cwd/cmds.txt                              Save New Del
 |     1 Help
 |
 |
@@ -389,7 +389,7 @@
 |
 |
 |
-|  /tmp/pardes-snap/leader/cwd/+Help New Del
+|  /tmp/pardes-snap/leader/cwd/+Help                                      New Del
 |     1 pardes builtins under SPC t
 |     2
 |     3 SPC t a   Ascii
@@ -410,7 +410,7 @@
 |
 == snap help-window grid=100x40 cursor=7,22
 |New Newcol Find Grep Help Tutor Dump NextColor Debug Kill
-|  /tmp/pardes-snap/leader/cwd/cmds.txt Save New Del
+|  /tmp/pardes-snap/leader/cwd/cmds.txt                              Save New Del
 |     1 Help
 |
 |
@@ -430,15 +430,15 @@
 |
 |
 |
-|  /tmp/pardes-snap/leader/cwd/+Help New Del
+|  /tmp/pardes-snap/leader/cwd/+Help                                      New Del
 |     1 pardes builtins under SPC w
 |     2
 |     3 SPC w h   Left            C-w h, C-w left
 |     4 SPC w j   Down            C-w j, C-w down
 |     5 SPC w k   Up              C-w k, C-w up
 |     6 SPC w l   Right           C-w l, C-w right
-|     7 SPC w t   Toggleterm
-|     8
+|     7
+|
 |
 |
 |
@@ -451,7 +451,7 @@
 |
 == snap help-language grid=100x40 cursor=7,22
 |New Newcol Find Grep Help Tutor Dump NextColor Debug Kill
-|  /tmp/pardes-snap/leader/cwd/cmds.txt Save New Del
+|  /tmp/pardes-snap/leader/cwd/cmds.txt                              Save New Del
 |     1 Help
 |
 |
@@ -471,7 +471,7 @@
 |
 |
 |
-|  /tmp/pardes-snap/leader/cwd/+Help New Del
+|  /tmp/pardes-snap/leader/cwd/+Help                                      New Del
 |     1 pardes builtins under SPC l
 |     2
 |     3 SPC l D   WsDiagnostics
@@ -492,7 +492,7 @@
 |
 == snap del-output grid=100x40 cursor=7,2
 |New Newcol Find Grep Help Tutor Dump NextColor Debug Kill
-|  /tmp/pardes-snap/leader/cwd/cmds.txt Save New Del
+|  /tmp/pardes-snap/leader/cwd/cmds.txt                              Save New Del
 |     1 Help
 |
 |