feat(observer): v15 AG Native chat relay — scanChatBodies dual strategy (#632)

- Add AG Native DOM path: #conversation + .leading-relaxed.select-text
- Keep Cascade path: [data-testid=conversation-view] + [data-step-index]
- Register #632 in known-issues.md (SDK+DOM both blocked for AG Native)
- Bump version 0.5.50 → 0.5.51
- Add DOM analysis helper scripts

extension/package.json

@@ -2,7 +2,7 @@
   "name": "gravity-bridge",
   "displayName": "Gravity Bridge",
   "description": "Discord-based unified approval system for Antigravity AI interactions.",
-  "version": "0.5.50",
+  "version": "0.5.51",
   "publisher": "variet",
   "engines": {
     "vscode": "^1.100.0"