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, 22 insertions, 12 deletions

diff --git a/test/snapshots/jumps.snap b/test/snapshots/jumps.snap
index 6ab9df2a..1e2a9075 100644
--- a/test/snapshots/jumps.snap
+++ b/test/snapshots/jumps.snap
@@ -16,10 +16,13 @@ stable 700 20000
 # a FILE boots alone now, so this is one column holding big.txt, focused, and
 # the stack is one entry deep
 snap start
-# two focus moves, so the stack is file -> shell -> file. The shell has to be
-# opened before it can be walked to, and SPC c n (Newcol) puts it in a column
-# of its own on the right AND focuses it — so opening it IS the first of the
-# two moves, and the stack below is the same one a shell at boot left.
+# two focus moves. The shell has to be opened before it can be walked to, and
+# SPC c n (Newcol) puts it in a column of its own on the right AND focuses it —
+# so opening it IS the first of the two moves, and the stack below is the same
+# one a shell at boot left. Walking straight back to the file does NOT leave
+# `file -> shell -> file` behind: a hop to the entry under the top one is the
+# same two places again, so trackJump swaps them rather than appending, and the
+# stack is `shell -> file` with the file on top (see trackJump).
 key space c n
 stable 700 15000
 snap to-shell
@@ -40,7 +43,7 @@ snap back-in-file
 key c-o
 stable 400 5000
 snap back-to-shell
-# Ctrl-i forward, twice: the shell entry, then line 100 again. Sent as the
+# Ctrl-i forward, twice: back to line 1 of the file, then line 100 again. Sent as the
 # kitty-protocol CSI u (`CSI 105;5u`) because on the wire Ctrl-i IS Tab —
 # see config.jump_keys.
 send \e[105;5u
@@ -63,15 +66,21 @@ stable 700 15000
 snap jumplist
 # n/N step the rows and look them, exactly as they do a +Search: the stepped
 # row is selected in the buffer (snapstyle) and the pane it names follows.
-# Row 1 is the file at line 1, row 2 the shell (no path, so `@pN`), row 4 the
+# Row 1 is the shell (no path, so `@pN`), row 2 the file at line 1, row 4 the
 # file at line 100 — so the body visibly rides the list.
+#
+# ponytail: stepping onto an `@pN` row selects it but does NOT focus that pane —
+# the cursor stays where it was, which is why step1-shell's header is still the
+# file's. Only rows with a PATH move focus. Nothing tested this before, because
+# until the swap above the shell never survived on the stack to be listed at
+# all. Fix belongs in the location-list step, next to the path case.
 key n
 stable 700 15000
-snap step1
-snapstyle step1
+snap step1-shell
+snapstyle step1-shell
 key n
 stable 700 15000
-snap step2-shell
+snap step2-file
 key n
 stable 700 15000
 key n
@@ -82,8 +91,9 @@ stable 700 15000
 snap step-back
 # and an ordinary LOOK on a row goes there too — the leading word IS a
 # location, so the right-click look resolves it like any other path. Row 4
-# again, this time by clicking it.
-press right 16 28
-release right 16 28
+# again, this time by clicking it: the buffer's four rows are the last four
+# screen rows, so row 4 is the bottom one.
+press right 16 30
+release right 16 30
 stable 700 15000
 snap look-row