T-207, first foundation piece of the Vim layer (T-65 epic). A
VimModeService (ChangeNotifier) owns the normal/insert/visual mode and
mirrors it into the keymap as mutually-exclusive vim.normal/vim.insert/
vim.visual scope flags. Those flags are the public mode interface: the
editor (T-206) will read them to decide insert-vs-command, and vim.yaml
(T-65) guards bindings with `when: vim.*`. Nothing reaches across the
builtin boundary into the service object.
The layer is gated on the active preset — the builtin.vim extension
ties VimModeService.enabled to app.keymap.preset and re-checks on every
keymap reload, so i/v/Esc never hijack input under non-Vim presets. Mode
commands (vim.mode.{normal,insert,visual}) carry no default binding for
the same reason; only vim.yaml binds keys to them. A status-bar item
shows `-- NORMAL --` etc. while enabled.
Exposes KeymapService on the extension context so the layer can publish
scope flags.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
jpmschweitzerandClaude Opus 4.8
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