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/clean-code/references/class-cohesion.md

@@ -0,0 +1,66 @@
+---
+title: Maintain Class Cohesion
+impact: MEDIUM
+impactDescription: enables extracting focused subclasses
+tags: class, cohesion, variables, methods
+---
+
+## Maintain Class Cohesion
+
+Classes should have a small number of instance variables. Each method should manipulate one or more of those variables. The more variables a method manipulates, the more cohesive the method is to its class.
+
+**Incorrect (low cohesion - methods use different variables):**
+
+```java
+public class Utility {
+    private Database db;
+    private EmailService email;
+    private Logger logger;
+    private Cache cache;
+
+    public void saveUser(User user) {
+        db.save(user);  // Only uses db
+        logger.log("Saved user");  // Only uses logger
+    }
+
+    public void sendNotification(String message) {
+        email.send(message);  // Only uses email
+    }
+
+    public Object getCached(String key) {
+        return cache.get(key);  // Only uses cache
+    }
+}
+// Each method uses different instance variables - low cohesion
+```
+
+**Correct (high cohesion - methods use shared variables):**
+
+```java
+public class Stack {
+    private int topOfStack = 0;
+    private List<Integer> elements = new LinkedList<>();
+
+    public int size() {
+        return topOfStack;  // Uses topOfStack
+    }
+
+    public void push(int element) {
+        topOfStack++;  // Uses topOfStack
+        elements.add(element);  // Uses elements
+    }
+
+    public int pop() throws EmptyStackException {
+        if (topOfStack == 0)
+            throw new EmptyStackException();
+        int element = elements.get(--topOfStack);  // Uses both
+        elements.remove(topOfStack);  // Uses both
+        return element;
+    }
+}
+// Every method uses the same instance variables - high cohesion
+```
+
+**When cohesion breaks down:** If a subset of methods only uses a subset of variables, extract those methods and variables into a separate class.
+
+Reference: [Clean Code, Chapter 10: Classes](https://www.oreilly.com/library/view/clean-code-a/9780136083238/)