[FEATURE] Vim mode: make NORMAL-mode keys rebindable (e.g. `/` opening history search)

Problem

In vim mode, / in NORMAL mode opens prompt-history search. Typing a slash command while you think you're in INSERT mode, probably the commonest vim-mode slip, lands in the search instead of the command menu, and what you type goes into the search query.

This can't be changed or turned off. The keybindings docs say vim keys aren't remappable through keybindings.json, and there is no vim-specific context. vimInsertModeRemaps covers only two-key INSERT-mode escapes.

Proposed solution

A VimNormal keybinding context, so NORMAL-mode keys can be rebound or unbound like everything else:

{ "context": "VimNormal", "bindings": { "/": null } }

It would also let Ctrl+R mean redo in NORMAL mode once that exists (#76684), without giving up Ctrl+R history search in INSERT mode.

A smaller alternative: a setting for what / does in NORMAL mode: history search (today), the slash-command menu (enter INSERT mode and type /), or nothing.

Related

#76684 (redo in NORMAL mode), #70705 and #62670 (docs for the / mapping).

Claude Code 2.1.295, macOS, Ghostty.