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/core/Tabs.prompt.md

@@ -0,0 +1,13 @@
+Underline tab strip for switching sibling views; active tab gets a 2px spruce underline.
+
+```jsx
+<Tabs
+  items={[
+    { id: 'board', label: 'Board', icon: 'square-kanban', count: 24 },
+    { id: 'gantt', label: 'Gantt', icon: 'chart-no-axes-gantt' },
+    { id: 'deps', label: 'Dependencies', icon: 'network' },
+  ]}
+  active={view}
+  onChange={setView}
+/>
+```