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, 14 insertions, 10 deletions

diff --git a/src/tutor.txt b/src/tutor.txt
index 1d01d626..1d51a4ac 100644
--- a/src/tutor.txt
+++ b/src/tutor.txt
@@ -227,12 +227,14 @@
    TTY     ($)  the REAL shell — prompts + typed input shown, and keys
                 go straight to the pty as terminal input.
 
- ESC:    insert -> normal; from body NORMAL it hops between the last
-         document and last terminal (the same Toggleterm as SPC w t).
+ ESC:    insert -> normal; from body NORMAL it hops to the pane you
+         were in before this one, whichever it was (the same Last as
+         SPC j j) — so held down it alternates between two panes.
          In raw TTY it still goes to the program.
- Ctrl-b: toggles TTY on a terminal by default; SHIFT-ESC is the same
-         toggle, where the host reports modifiers on Escape. Those are
-         the ONLY ways in or out.
+ Ctrl-b: toggles TTY on a terminal, and is the only way back OUT of it.
+         SHIFT-ESC gets you IN, and once in TTY it does what ESC does in
+         normal mode — hops away, leaving this pane in TTY so coming
+         back lands you in the program you left.
          Use `pardes --tty-toggle=g` (or another letter) to make Ctrl-g
          the toggle instead. Entering is tty-native: if the shell is at
          a prompt and your modal cursor sits on the input line, it first
@@ -494,8 +496,9 @@
    Ctrl-w h/j/k/l   focus the pane left/down/up/right (SPC w h/j/k/l
                     does the same; Ctrl-w also reaches a tty pane,
                     where SPC belongs to the shell)
-   Esc              hop between the last document and last terminal
-                    (body normal mode; the same builtin as SPC w t)
+   Esc              hop to the pane you were in before this one, so
+                    held down it alternates between two (body normal
+                    mode; the same builtin as SPC j j)
    Alt-n            new terminal below the active one
    Alt-c            move the active terminal into a fresh column
 
@@ -523,8 +526,9 @@
                     letters join the matcher's glyph set
    SPC s d / s r    Dump / Restore the session
    SPC w h/j/k/l    Left/Down/Up/Right: focus the pane that way
-   SPC w t          Toggleterm: hop between the last document you
-                    looked at and the last terminal, and back
+   SPC j o / j i    Back / Forward: walk the jump history
+   SPC j j          Last: the pane you were in before this one — what
+                    body-normal ESC runs, so it alternates
 
  `?` works at ANY depth: SPC ? lists everything, SPC h ? lists only
  what the "h" group holds. Help writes into a "+Help" OUTPUT BUFFER,
@@ -564,7 +568,7 @@
                 SPC = the leader: a key path runs a builtin (SPC ? lists
                 them; SPC k Kill, SPC d Del, SPC f s Save, SPC f f Find,
                 SPC f n New,
-                SPC w hjkl focus, SPC w t file <-> terminal)
+                SPC w hjkl focus, SPC j j the pane before this one)
 
  vs Helix: no multi-cursor; selection is LINE-first (x), plus v chars.
  vs Vim:  no verb+noun (dw); motions only move; body-normal Esc hops focus.