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.

2 files changed, 5 insertions, 4 deletions

diff --git a/docs/design.typ b/docs/design.typ
index c6f0e73e..75c89812 100644
--- a/docs/design.typ
+++ b/docs/design.typ
@@ -201,8 +201,9 @@ the source (cursor row kept visible); dying pane's weight absorbed by one
 sibling; emptied column hands width to a neighbor; border-drag resize on a
 pane's own trailing edge (v and h), hover shows `╎`/`╌` glyph-only hints;
 move-drag via the gutter box with preview; Alt-n new shell below, Alt-c move
-pane to new column; Ctrl-w h/j/k/l directional focus; body-normal Esc toggles
-between the latest document and terminal (the same builtin as SPC w t);
+pane to new column; Ctrl-w h/j/k/l directional focus; body-normal Esc hops to
+the pane you were in before this one, alternating between two (the same
+builtin as SPC j j);
 `--tty` single-pane mode.
 
 *Mouse.* Left: select (block, stays highlighted after drag, pins cursor,
diff --git a/docs/helix-keys.md b/docs/helix-keys.md
index 23f8f926..13a9a279 100644
--- a/docs/helix-keys.md
+++ b/docs/helix-keys.md
@@ -83,7 +83,7 @@ with a reason in `test/hxcases/waivers.jsonl`.
 | `y` | yank selection; bare cursor yanks the 1-wide selection (char under cursor) | line-yank vim-ism removed (phase 5); yank keeps selection AND cursor (helix). Also emits `set_clipboard` (OSC 52 out) | helix-verified |
 | `u` / `U` | undo / redo | restores the pre-edit selection (helix); snapshot granularity, no `Alt-u`/`Alt-U` history walking (skipped) | helix-verified |
 | `p` (normal) | paste the core's yank register after the selection | helix default-register semantics; yank still mirrors OUT via OSC 52 (`set_clipboard`) but `p` never reads the system clipboard back — most terminals refuse the OSC 52 read, which left `p` a silent no-op | helix-verified |
-| `Esc` (body normal) | clear a pending modal prefix / exit select mode, keeping the selection, then run `Toggleterm`: hop between the most recently focused document and terminal, exactly like `SPC w t` | Pardes-specific focus binding layered on helix's cleanup. A leader path, tag, topbar or search owns Esc while it is active; raw tty forwards it | pardes-specific (cleanup helix-verified) |
+| `Esc` (body normal) | clear a pending modal prefix / exit select mode, keeping the selection, then run `Last`: hop to the pane you were in before this one, whichever kind it was, exactly like `SPC j j` — so held down it alternates between two panes, two files as readily as a file and its shell | Pardes-specific focus binding layered on helix's cleanup. A leader path, tag, topbar or search owns Esc while it is active; raw tty forwards it | pardes-specific (cleanup helix-verified) |
 | `Esc` (insert) | back to normal mode, cursor right after the insertion (no vim left-step) | | helix-verified |
 | `Enter` (normal) | acme **look** chord: EXPLICIT selection, else file-ish word under cursor | pardes-specific, keep (helix normal-mode Enter unbound). Covers helix `gf`. Implicit motion residue falls back to the cursor word | pardes-specific |
 | `Tab` (normal) | acme **execute** chord | pardes-specific, keep; explicit-selection rule as Enter | pardes-specific |
@@ -92,7 +92,7 @@ with a reason in `test/hxcases/waivers.jsonl`.
 | `Ctrl-w` + `h/j/k/l`/arrows | directional pane focus prefix — normal/tty modes only | pardes' own window handling (helix window mode skipped, section C). Runs the SAME `Left`/`Down`/`Up`/`Right` builtins `SPC w h/j/k/l` runs; kept alongside the leader because a pane in raw **tty** mode never sees `SPC` (the shell owns it), so this is the only keyboard way out of one. Insert mode owns `Ctrl-w` = delete-word-back, so a tag being TYPED into swallows it; from a tag in normal mode (`:`) it moves focus to the neighbour's BODY, while the bare letters `h/j/k/l` there move to its TAGLINE (next row) | pardes-specific |
 | `Alt-n` | new terminal below (any mode) | shadows helix `Alt-n` TS sibling-select — skipped anyway (tree-sitter) | pardes-specific |
 | `Alt-c` | move active terminal to a fresh column (any mode) | helix `Alt-c` is change-noyank; the pardes window op wins (do-not-touch contract). `Alt-d` + `i` covers the behavior | waived (`alt-c-window-op`) |
-| `Space` (normal, body) | the pardes LEADER: a key path from here runs a BUILTIN with no arguments — the same builtins the topbar and the tags hold. `SPC k` Kill, `SPC d` Del, `SPC f s` Save, `SPC f n` New (an empty temporary file focused in the calling pane's column), `SPC f f` Find (fd over the pane's directory, results into `+Search`), `SPC f g` Grep (grep -R over the CONTENTS of every pane's directory, the ones another pane already covers dropped, rows relative to the asking pane's own directory, results into `+Search`; like Find it takes an ARGUMENT — `Grep foo` executed, or a selection chorded onto the word, searches that and skips the input), `SPC h t` Tutor, `SPC c n`/`SPC c d` Newcol/Delcol, `SPC t d/c/n/r` Debug/Colors/NextColor/Crt, `SPC t t` ThemeSel (the whole theme ring as `Theme <name>` rows in an output buffer — the one list whose rows are COMMANDS, so n/N execute each row instead of looking it and stepping is a live preview), `SPC t p/l/a` Petscii/Palette/Ascii (an image pane's renderer toggles — the words its tag used to spell out, so the bar stays a bar), `SPC s d`/`SPC s r` Dump/Restore, `SPC w h/j/k/l` Left/Down/Up/Right (directional pane focus — the `Ctrl-w` prefix's four moves as builtins), `SPC w t` Toggleterm (focus hops between the most recently focused document — file, image or `+Search`/`+Help` buffer — and the most recently focused terminal; the same key hops back). `?` at ANY depth opens the Help builtin listing what the prefix can still reach (`SPC ?` = all, `SPC h ?` = the docs group), into a `+Help` output buffer. The pending path shows at the right edge of the active pane's tag; Esc — or any unmapped key — abandons it | helix spends Space on pickers/LSP (section C); pardes has neither, and acme's builtins are what a leader is for. Enum-derived: the paths, the Help lines and the execute dispatch all fold out of one `Builtin` enum at comptime. Normal mode on a BODY only — tags are always insert, tty keys belong to the program | pardes-specific |
+| `Space` (normal, body) | the pardes LEADER: a key path from here runs a BUILTIN with no arguments — the same builtins the topbar and the tags hold. `SPC k` Kill, `SPC d` Del, `SPC f s` Save, `SPC f n` New (an empty temporary file focused in the calling pane's column), `SPC f f` Find (fd over the pane's directory, results into `+Search`), `SPC f g` Grep (grep -R over the CONTENTS of every pane's directory, the ones another pane already covers dropped, rows relative to the asking pane's own directory, results into `+Search`; like Find it takes an ARGUMENT — `Grep foo` executed, or a selection chorded onto the word, searches that and skips the input), `SPC h t` Tutor, `SPC c n`/`SPC c d` Newcol/Delcol, `SPC t d/c/n/r` Debug/Colors/NextColor/Crt, `SPC t t` ThemeSel (the whole theme ring as `Theme <name>` rows in an output buffer — the one list whose rows are COMMANDS, so n/N execute each row instead of looking it and stepping is a live preview), `SPC t p/l/a` Petscii/Palette/Ascii (an image pane's renderer toggles — the words its tag used to spell out, so the bar stays a bar), `SPC s d`/`SPC s r` Dump/Restore, `SPC w h/j/k/l` Left/Down/Up/Right (directional pane focus — the `Ctrl-w` prefix's four moves as builtins), `SPC j o`/`SPC j i`/`SPC j j`/`SPC j l` Back/Forward/Last/Jumplist (the jump stack: walk it back, walk it forward, hop to the pane before this one — what body-normal Esc runs — and read the stack as a clickable buffer). `?` at ANY depth opens the Help builtin listing what the prefix can still reach (`SPC ?` = all, `SPC h ?` = the docs group), into a `+Help` output buffer. The pending path shows at the right edge of the active pane's tag; Esc — or any unmapped key — abandons it | helix spends Space on pickers/LSP (section C); pardes has neither, and acme's builtins are what a leader is for. Enum-derived: the paths, the Help lines and the execute dispatch all fold out of one `Builtin` enum at comptime. Normal mode on a BODY only — tags are always insert, tty keys belong to the program | pardes-specific |
 | `/` then `n`/`N` (any pane) | pardes' own plain-substring search into a `+Search` output buffer, n/N walk the result rows and look them (EXPLICIT selections) | KEEP, do not touch; not in the corpus (helix `/` is regex search) | pardes-specific |
 | `n`/`N` (terminal panes, no search armed) | lookable-token motion over scrollback (EXPLICIT selections) | KEEP, do not touch | pardes-specific |
 | insert: printable text | file: real edit; terminal: typed run splice | | helix-verified (file) |