fix(ext): spec compliance fixes — stagnation recovery, comet fallback, quote anti-trigger, types, package.json

- trigger-detector: fix quote anti-trigger (only block if trigger exclusively in quotes)
- trigger-detector: add uncertainty fallback pattern (goal is/为 + deliverable)
- trigger-detector: add 'fix bug' to trivial keywords
- index.ts: implement stagnation auto-recovery injection
- index.ts: implement comet fallback when openspec not available
- index.ts: replace 'any' types with ExtensionContext
- index.ts: wire consecutiveStagnations counter
- Add package.json for extension discovery

.pi/extensions/goal-driven-loop/package.json

@@ -0,0 +1,8 @@
+{
+  "name": "goal-driven-loop",
+  "version": "1.0.0",
+  "private": true,
+  "pi": {
+    "extensions": ["./index.ts"]
+  }
+}