ship the Vim keymap preset

T-65 — the capstone of the Vim epic. assets/keymaps/vim.yaml binds the
muscle-memory set guarded on vim.normal/insert/visual: hjkl/w/b/e/0/$/^/
gg/G motions, x/dd/dw/D/yy/p/P/cc/cw edits, i/a/I/A/o/O insert entries,
v + d/y/c in visual, Esc back to normal, and counts via the matcher. App
shortcuts (palette, find, zoom) are carried in the preset so they survive
under Vim.

The editor now feeds Shift chords to the matcher (Vim's capitals: G, D,
A, P, $) while still bubbling Ctrl/Alt/Meta to the global handler. The
keybindings-ui stub gains palette commands (`Keymap: Vim` / `Keymap:
Default`) to switch presets — the user-facing way to turn Vim on.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

CHANGELOG.md

@@ -18,6 +18,10 @@ heading, and (b) bumping `pubspec.yaml` `version:` in the same commit.
 
 ### Added
 
+- Vim keymap preset: a modal editor (normal/insert/visual) with hjkl/w/b/e
+  motions, dd/dw/x/D/yy/p/cc/cw edits, counts (`5j`), visual-range d/y/c, and
+  a status-bar mode indicator. Switch presets from the palette (`Keymap: Vim`
+  / `Keymap: Default`). Built on a new keymap key-sequence layer (D-82). (T-65)
 - Search-and-replace across the workspace: enter a replacement in the search
   panel to preview each rewritten line, then Replace all (regex capture groups
   supported). Guarded by a clean-git-tree gate — git is the undo — and a