fix(bridge): rawRPC direct polling + SDK analysis docs + trial-and-error log

- Root cause: getDiagnostics.lastStepIndex is stale, SDK EventMonitor cannot detect real-time step changes
- Fix: Direct rawRPC('GetCascadeTrajectorySteps') polling every 5s
- Relay: PLANNER_RESPONSE, NOTIFY_USER, TASK_BOUNDARY, WAITING steps
- Added: docs/discord-bridge-analysis.md (full SDK architecture analysis)
- Added: docs/devlog/entries/20260308-003.md (trial-and-error history)
- Added: antigravity-sdk-main/ source reference
- Vikunja: #252 done, #253 created, #251 commented

antigravity-sdk-main/.gitignore

@@ -0,0 +1,15 @@
+node_modules/
+dist/
+docs-site/
+*.tsbuildinfo
+.DS_Store
+
+# Internal reference — not for public repo
+GEMINI.md
+docs/implementation-plan.md
+docs/internals.md
+scripts/
+
+# Extensions (separate repo)
+example-extension/
+xray-extension/