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/err-provide-context.md

@@ -0,0 +1,53 @@
+---
+title: Provide Context with Exceptions
+impact: HIGH
+impactDescription: enables rapid root cause identification
+tags: err, context, messages, debugging
+---
+
+## Provide Context with Exceptions
+
+Each exception should provide enough context to determine the source and location of an error. Create informative error messages that describe the operation that failed and the type of failure.
+
+**Incorrect (no context):**
+
+```java
+throw new Exception("Error occurred");
+
+throw new RuntimeException("Failed");
+
+throw new DataAccessException("Query failed");
+
+// Stack trace alone doesn't tell you which order, which customer
+catch (SQLException e) {
+    throw new RuntimeException(e);
+}
+```
+
+**Correct (rich context):**
+
+```java
+throw new OrderProcessingException(
+    String.format("Failed to process order %s for customer %s: %s",
+        orderId, customerId, "Insufficient inventory for item SKU-12345"));
+
+throw new ConfigurationException(
+    "Cannot load configuration from " + configPath +
+    ". Expected format: YAML. Check file permissions and syntax.");
+
+catch (SQLException e) {
+    throw new DataAccessException(
+        String.format("Failed to insert order %s into table %s. " +
+            "Constraint violated: %s",
+            order.getId(), "orders", e.getMessage()),
+        e);  // Preserve original exception
+}
+```
+
+**Include in exception messages:**
+- What operation was being attempted
+- What data was involved (IDs, names, quantities)
+- Why it failed (the specific error condition)
+- Preserve the original exception when wrapping
+
+Reference: [Clean Code, Chapter 7: Error Handling](https://www.oreilly.com/library/view/clean-code-a/9780136083238/)