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, 8 insertions, 8 deletions

diff --git a/test/snapshots/lspdebug.golden b/test/snapshots/lspdebug.golden
index b34a264f..ce90c19d 100644
--- a/test/snapshots/lspdebug.golden
+++ b/test/snapshots/lspdebug.golden
@@ -1,6 +1,6 @@
 == snap opened grid=120x44 cursor=7,2
 |New Newcol Find Grep Help Tutor Dump NextColor Debug Kill
-|  /tmp/pardes-snap/lspdebug/cwd/z.zig Save New Del
+|  /tmp/pardes-snap/lspdebug/cwd/z.zig                                                   Save New Del
 |     1 const std = @import("std");
 |     2
 |     3 fn helper() u32 {
@@ -45,7 +45,7 @@
 |
 == snap ctrlclick grid=120x44 cursor=15,4
 |New Newcol Find Grep Help Tutor Dump NextColor Debug Kill
-|  /tmp/pardes-snap/lspdebug/cwd/z.zig Save New Del
+|  /tmp/pardes-snap/lspdebug/cwd/z.zig                                                   Save New Del
 |     1 const std = @import("std");
 |     2
 |     3 fn helper() u32 {
@@ -90,7 +90,7 @@
 |
 == snap plainclick grid=120x44 cursor=21,9
 |New Newcol Find Grep Help Tutor Dump NextColor Debug Kill
-|  /tmp/pardes-snap/lspdebug/cwd/z.zig Save New Del
+|  /tmp/pardes-snap/lspdebug/cwd/z.zig                                                   Save New Del
 |     1 const std = @import("std");
 |     2
 |     3 fn helper() u32 {
@@ -135,7 +135,7 @@
 |
 == snap why grid=120x44 cursor=7,4
 |New Newcol Find Grep Help Tutor Dump NextColor Debug Kill
-|  /tmp/pardes-snap/lspdebug/cwd/z.zig Save New Del
+|  /tmp/pardes-snap/lspdebug/cwd/z.zig                                                   Save New Del
 |     1 const std = @import("std");
 |     2
 |     3 fn helper() u32 {
@@ -168,7 +168,7 @@
 |
 |
 |
-|  /tmp/pardes-snap/lspdebug/cwd/+Lsp New Del
+|  /tmp/pardes-snap/lspdebug/cwd/+Lsp                                                         New Del
 |     1 lsp explain — the definition query at byte 29 of z.zig
 |     2
 |     3 zig lib dir: /usr/lib/zig (open) — `std` imports resolve
@@ -180,7 +180,7 @@
 |     9 0 row(s)
 == snap info grid=120x44 cursor=7,4
 |New Newcol Find Grep Help Tutor Dump NextColor Debug Kill
-|  /tmp/pardes-snap/lspdebug/cwd/z.zig Save New Del
+|  /tmp/pardes-snap/lspdebug/cwd/z.zig                                                   Save New Del
 |     1 const std = @import("std");
 |     2
 |     3 fn helper() u32 {
@@ -197,7 +197,7 @@
 |
 |
 |
-|  /tmp/pardes-snap/lspdebug/cwd/+Lsp New Del
+|  /tmp/pardes-snap/lspdebug/cwd/+Lsp                                                         New Del
 |     1 backend: zls-inproc
 |     2 zls: 0.16.1-dev+3e0d0820 (compiled in — no server process, no JSON-RPC)
 |     3 zig lib dir: /usr/lib/zig  [OK]
@@ -213,7 +213,7 @@
 |    10   mvzr           /home/goblin/00-projects/0x4200.cafe/02-pardes-code/zig-pkg/mvzr-0.3.9-ZSOky6t2AQCA7efmm5EYbPb5↩
 |       sOdbXa4EFsUgYbQ6hZv9/src/mvzr.zig
 |    11   mupdf          /home/goblin/00-projects/0x4200.cafe/02-pardes-code/src/pdf.zig
-|  /tmp/pardes-snap/lspdebug/cwd/+Lsp New Del
+|  /tmp/pardes-snap/lspdebug/cwd/+Lsp                                                         New Del
 |     1 lsp explain — the definition query at byte 29 of z.zig
 |     2
 |     3 zig lib dir: /usr/lib/zig (open) — `std` imports resolve