refactor(cleanup): v0.5.0 Collector 제거 + dead code 정리 + HttpBridgeContext 버그 수정

- DELETE collector.py (523줄)
- main.py: BOT_MODE=remote 분기 제거
- gateway.py: Collector REST 6개 endpoint 제거 (311→168줄)
- bridge.py: RemoteTransport 제거 (480→270줄)
- config.py: REMOTE_BRIDGE_URL 제거
- extension.ts: dead code 4개 + stale module vars 제거
- step-probe.ts: getStepProbeContext() 추가, autoApproveEnabled 제거
- FIX: HttpBridgeContext stale primitive (getter 패턴으로 수정)
- ADD: extension.log rotation (10MB→2MB tail)
- docs: architecture.md, tech-stack.md, known-issues.md 업데이트

extension/package.json

@@ -2,7 +2,7 @@
     "name": "gravity-bridge",
     "displayName": "Gravity Bridge",
     "description": "Antigravity ↔ Discord 브리지 연동 확장",
-    "version": "0.4.6",
+    "version": "0.5.0",
     "publisher": "variet",
     "engines": {
         "vscode": "^1.100.0"