Silence render-disposed spam, unbreak bundled skills, drop board wake

Three independently ugly bugs that all fed the same log flood:

* Electron's `WebFrameMain.send` writes every "Render frame was disposed"
  to stderr via `console.error`. When the worker fans a second
  agent-event past a reloading renderer, we produced thousands of
  identical lines and stalled the main loop on stderr I/O. Added a
  `mainFrame.detached` guard so the send is short-circuited before
  Electron's own catch block fires, and installed a targeted filter in
  `suppress-warnings.ts` (now actually imported from the entry point)
  so the specific `console.error("Error sending from webFrameMain:"…)`
  noise never reaches the terminal. Any other payload still surfaces.

* `dispatchAgentMessage` accepted the human-reader sentinel as a wake
  target when an agent replied to `__board__` — `wakeAgentIfPossible`
  then called `db.getAgent("__board__")`, threw, and the dispatcher
  kept repeating on every send. Strip `HUMAN_SENDER_ID` at
  `resolveMessageWakeTargets`, and keep a defense-in-depth guard in the
  heartbeat so a stray caller (future automation fan-out) cannot
  reintroduce the crash.

* Pi's skills loader rejects any SKILL.md whose frontmatter `name`
  diverges from its parent directory. The four bundled `my-writing-style`
  copies declared `name: writing-style-skill`, so every install emitted
  a warning and dropped the skill. They also lived as orphan gitlinks
  (mode 160000 without .gitmodules), and the global `*.md` gitignore
  hid every other SKILL.md from version control. Fixed the frontmatter
  to match the dir, converted the dangling submodules to plain trees,
  and allowlisted `builtin-skills/**/*.md` so a fresh clone carries the
  catalogue instead of silently losing it.

builtin-skills/software-engineer/mobile-development/references/MOBILE_GUIDE.md

@@ -0,0 +1,73 @@
+# Mobile Development Guide for Cloudflare
+
+## PWA on Cloudflare Pages
+
+```json
+// manifest.json
+{
+  "name": "My PWA",
+  "short_name": "PWA",
+  "start_url": "/",
+  "display": "standalone",
+  "background_color": "#ffffff",
+  "theme_color": "#f38020",
+  "icons": [
+    { "src": "/icon-192.png", "sizes": "192x192", "type": "image/png" },
+    { "src": "/icon-512.png", "sizes": "512x512", "type": "image/png" }
+  ]
+}
+```
+
+## Service Worker with Cloudflare
+
+```typescript
+// sw.ts - Offline-first strategy
+const CACHE_NAME = 'v1';
+const OFFLINE_URL = '/offline.html';
+
+self.addEventListener('install', (event) => {
+  event.waitUntil(
+    caches.open(CACHE_NAME).then((cache) => {
+      return cache.addAll([OFFLINE_URL, '/', '/styles.css']);
+    })
+  );
+});
+
+self.addEventListener('fetch', (event) => {
+  event.respondWith(
+    fetch(event.request).catch(() => caches.match(OFFLINE_URL))
+  );
+});
+```
+
+## Mobile API with Workers
+
+```typescript
+// Optimized for mobile clients
+export default {
+  async fetch(request: Request, env: Env) {
+    const userAgent = request.headers.get('User-Agent') || '';
+    const isMobile = /Mobile|Android|iPhone/i.test(userAgent);
+
+    return Response.json({
+      data: await getData(env),
+      optimized: isMobile ? 'mobile' : 'desktop'
+    }, {
+      headers: {
+        'Cache-Control': isMobile ? 'max-age=300' : 'max-age=3600'
+      }
+    });
+  }
+};
+```
+
+## Deployment
+
+```bash
+# Deploy to Cloudflare Pages
+npx wrangler pages deploy dist --project-name=my-pwa
+```
+
+---
+
+*Cloudflare Plugin - Mobile Development Skill*