feat(api): add backend with kanban, docs store, and orchestrator

Introduce the @void-nav/api Hono + SQLite backend that powers the docs site:
a persisted implementation board (kanban), a custom documentation-pages store
with AI beautify, and an agentic orchestrator that runs `pi` agents per card.

The orchestrator spawns `pi --mode rpc` inside an isolated git worktree per run,
streams slim events over SSE, and lets the agent drive the board/docs via
token-gated internal endpoints (all SQLite writes stay in-process). Interrupted
runs are reconciled to "stopped" on boot.

Workspace wiring: root `dev:api`/`dev:web` scripts with `concurrently`, the
docs Vite `/api` proxy, and `.worktrees/` gitignore.

package.json

@@ -5,7 +5,9 @@
   "type": "module",
   "scripts": {
     "dev": "bash scripts/dev.sh",
+    "dev:api": "pnpm --filter @void-nav/api dev",
     "dev:docs": "pnpm --filter @void-nav/docs dev --port 5173",
+    "dev:web": "concurrently -n api,docs -c blue,green \"pnpm dev:api\" \"pnpm dev:docs\"",
     "dev:site": "pnpm --filter @void-nav/site dev --port 5174",
     "dev:game": "echo 'Game app not yet created. Run pnpm create-vite apps/game to scaffold.'",
     "build": "pnpm -r --if-present build",
@@ -13,7 +15,8 @@
   },
   "devDependencies": {
     "@commitlint/cli": "^19.6.1",
-    "@commitlint/config-conventional": "^19.6.0"
+    "@commitlint/config-conventional": "^19.6.0",
+    "concurrently": "^10.0.3"
   },
   "packageManager": "pnpm@9.15.0"
 }