setup: workspace, dev deps, and project-local extension install

- Add pnpm-workspace.yaml for monorepo
- Add @mariozechner/pi-coding-agent as root devDependency (TS types)
- Create .pi/settings.json with local package reference
- Extension auto-loads and hot-reloads via /reload

packages/pi-turn-limit/package.json

@@ -4,11 +4,11 @@
   "description": "Pi coding agent extension to limit number of turns taken by a model",
   "type": "module",
   "exports": {
-    ".": "./src/index.ts"
+    ".": "./src/turn-limit.ts"
   },
   "keywords": ["pi-package"],
   "pi": {
-    "extensions": ["src/index.ts"]
+    "extensions": ["src/turn-limit.ts"]
   },
   "peerDependencies": {
     "@mariozechner/pi-coding-agent": "*"