repo: dripnex/plugin-vim — extract vim mode

[tomymaritano]

Context

src/renderer/plugins/vimMode.tsx (100 LOC, currently a stub) becomes a satellite — the direct mirror of inkdrop-vim. Good candidate to hand to a community contributor later.

Acceptance criteria

• Repo from plugin-template; npm @dripnex/plugin-vim; runtime id dripnex-vim
• Uses editor API (CodeMirror extension registration) + keymaps registry from plugin-api
• Replaces the stub with @replit/codemirror-vim (or equivalent) — actually functional vim, not a stub
• Toggleable; off by default; e2e: enable → modal editing works (i/Esc/:w smoke)

Depends on

Keymaps registry + editor API (Q1).