fix: remove dead delete+recreate and pin code, add poll fallback test

Phase 1 cleanup:
- Remove deletePost() method (dead code, replaced by PUT in-place updates)
- Remove _postInfo Map tracking (no longer needed)
- Remove pin/unpin API calls from watcher-manager.js (incompatible with PUT updates)
- Add JSDoc note on (edited) label limitation in _flushUpdate()
- Add integration test: test/integration/poll-fallback.test.js
- Fix addSession() lastOffset===0 falsy bug (0 was treated as 'no offset')
- Fix pre-existing test failures: add lastOffset:0 where tests expect backlog reads
- Fix pre-existing session-monitor test: create stub transcript files
- Fix pre-existing status-formatter test: update indent check for blockquote format
- Format plugin/ files with Prettier (pre-existing formatting drift)

plugin/webapp/package.json

@@ -0,0 +1,20 @@
+{
+  "name": "com.openclaw.livestatus-webapp",
+  "version": "0.1.0",
+  "private": true,
+  "scripts": {
+    "build": "webpack --mode=production",
+    "dev": "webpack --mode=development --watch"
+  },
+  "devDependencies": {
+    "css-loader": "^6.11.0",
+    "style-loader": "^3.3.4",
+    "ts-loader": "^9.5.4",
+    "typescript": "^5.9.3",
+    "webpack": "^5.105.4",
+    "webpack-cli": "^5.1.4"
+  },
+  "dependencies": {
+    "@types/react": "^18.2.0"
+  }
+}