[oller]

Why

Resolves #251.

Vim considers command-line mode a distinct primary mode, but vim-mode-change was not emitted when entering or exiting command-line prompts (:, /, ?). Consumers had to track dialog state manually.

What changed

• Emit vim-mode-change with { mode: "command" } when an interactive prompt opens.
• Emit vim-mode-change with the restored mode (normal, visual, or insert) when the prompt closes or is cancelled via Escape.
• Filter out non-interactive notification banners (such as yank confirmations) so only prompts with input fields trigger command mode.
• Export VimMode, VimSubMode, and VimModeChangeEvent discriminated union types, replacing any in the mode change listener.
• Update on_mode_change test suite to assert command mode transitions.

Test plan

• Run pnpm run typecheck to verify strict TypeScript compilation.
• Run pnpm test to verify all 711 tests pass.
• Verify on_mode_change passes when entering command mode with : and exiting with both y\n and <Esc>.

[oller]

I think the failing workflow is unrelated. I've tried to keep this PR as succinct and non-slop as possible. Tests added, happy to revise, let me know your thoughts.