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/bound-learning-tests.md

@@ -0,0 +1,59 @@
+---
+title: Write Learning Tests for Third-Party Code
+impact: MEDIUM
+impactDescription: catches 90%+ of breaking changes in dependency upgrades before production
+tags: bound, boundary, learning-tests, third-party, testing
+---
+
+## Write Learning Tests for Third-Party Code
+
+When integrating a third-party library, write small tests that verify your understanding of how the API works. These tests serve double duty: they help you learn the API, and they act as a safety net when upgrading the library.
+
+**Incorrect (learning by trial and error in production code):**
+
+```java
+// Experimenting directly in application code
+public void importCustomerRecord(String json) {
+    // Does Gson handle null fields? Let's find out...
+    Gson gson = new Gson();
+    CustomerRecord record = gson.fromJson(json, CustomerRecord.class);
+    // Does this throw or return null for missing fields?
+    // Who knows — we'll find out in production
+}
+```
+
+**Correct (learning tests verify assumptions):**
+
+```java
+@Test
+public void gsonShouldDeserializeNullFieldsAsNull() {
+    Gson gson = new Gson();
+    Data data = gson.fromJson("{}", Data.class);
+
+    assertNull(data.getName());
+}
+
+@Test
+public void gsonShouldHandleMalformedJson() {
+    Gson gson = new Gson();
+
+    assertThrows(JsonSyntaxException.class,
+        () -> gson.fromJson("{invalid", Data.class));
+}
+
+@Test
+public void gsonShouldIgnoreUnknownFields() {
+    Gson gson = new Gson();
+    Data data = gson.fromJson("{\"name\":\"test\",\"unknown\":true}", Data.class);
+
+    assertEquals("test", data.getName());
+}
+```
+
+**Benefits:**
+- Free education on the API's behavior
+- When you upgrade the library, these tests break first — before your production code does
+- Documents exactly which behaviors your code relies on
+- Takes minutes to write but saves hours of debugging
+
+Reference: [Clean Code, Chapter 8: Boundaries](https://www.oreilly.com/library/view/clean-code-a/9780136083238/)