Scaffold CommiTea: yarn workspaces, Electron shell, core label schema, design system

- apps/desktop: electron-vite + React + Tailwind mapped onto design tokens
  (preflight off; tokens/base.css owns the reset); boots to a Reginald
  placeholder proving fonts/tokens/core wiring
- packages/core: pure TS; gitea label schema (est/*, p/*, deadline/hard)
  with pessimistic conflict resolution + 15 unit tests
- docs/design: full design handoff (tokens, 16 component contracts,
  interactive 14-screen prototype, Reginald voice rules)
- docs/PLAN.md: product plan (purity rule, pm-state repo, deterministic
  scheduler + Monte Carlo, directive log)
- Deliberate deviation from novelpad stack: no ElectricSQL/PGlite — local
  store is a rebuildable cache over gitea REST/webhooks (better-sqlite3
  in main process, arriving in P1)

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

docs/design/components/forms/Checkbox.prompt.md

@@ -0,0 +1,5 @@
+Checkbox for multi-selects and settings toggles that read as options (use `Switch` for live on/off state).
+
+```jsx
+<Checkbox label="Include closed issues" checked={inc} onChange={(e) => setInc(e.target.checked)} />
+```