fix(extension): UTF-8 encoding + noise filter enhancement (v0.5.39)

- http-bridge.ts: add req.setEncoding('utf8') to all POST handlers
  to fix Korean text corruption in pending/chat/dump payloads
- observer-script.ts: add inline pre-strip in cleanLines() for
  Material icon names concatenated by textContent without newlines
- observer-script.ts: apply cleanLines() to codeText extraction
- known-issues: document UTF-8 encoding and noise filter issues

extension/package.json

@@ -2,7 +2,7 @@
   "name": "gravity-bridge",
   "displayName": "Gravity Bridge",
   "description": "Discord-based unified approval system for Antigravity AI interactions.",
-  "version": "0.5.38",
+  "version": "0.5.39",
   "publisher": "variet",
   "engines": {
     "vscode": "^1.100.0"