chore: remove computer use (re-applied after main merge)

The merge of main into this branch (0907d87) hit a modify/delete conflict
for the computer-use module — main removed it in 6761f31 while this branch
had extended it — and the conflict was resolved by keeping the branch's
copies, silently resurrecting the whole feature.

This re-applies 6761f31's removal on top of the browser-use work:
- deletes the computer-use server module, client panel, settings tab,
  desktop-agent websocket service, electron computerAgent, and the
  computer-semantics build scripts
- strips computer-use wiring from shared files (server/index.js, electron
  launcher/main, MainContent, settings, i18n) while preserving browser-use
- removes src/constants/featureFlags.ts (existed only for the CU menu flag)

browser-use (camoufox/noVNC) is untouched. typecheck passes.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

package.json

@@ -29,13 +29,10 @@
   "scripts": {
     "dev": "concurrently --kill-others \"npm run server:dev\" \"npm run client\"",
     "server": "node dist-server/server/index.js",
-    "preserver:dev": "npm run build:semantics",
     "server:dev": "tsx --tsconfig server/tsconfig.json server/index.js",
-    "preserver:dev-watch": "npm run build:semantics",
     "server:dev-watch": "tsx watch --tsconfig server/tsconfig.json server/index.js",
     "client": "vite",
     "desktop": "electron electron/main.js",
-    "predesktop:dev": "npm run build:semantics",
     "desktop:dev": "cross-env ELECTRON_DEV_URL=http://127.0.0.1:5173 electron electron/main.js",
     "desktop:stage": "node scripts/release/prepare-desktop-app.js",
     "desktop:pack": "npm run build && npm run desktop:stage && electron-builder --projectDir .desktop-build/desktop-app --dir",
@@ -43,12 +40,10 @@
     "desktop:dist:win": "npm run build && npm run desktop:stage && electron-builder --projectDir .desktop-build/desktop-app --win nsis",
     "server:bundle": "npm run build && node scripts/release/build-server-bundle.js",
     "desktop:icon:mac": "node electron/scripts/generate-macos-icon.js",
-    "build": "npm run build:semantics && npm run build:client && npm run build:server",
+    "build": "npm run build:client && npm run build:server",
     "build:client": "vite build",
-    "build:semantics": "node scripts/build-computer-semantics.mjs",
     "prebuild:server": "node -e \"require('node:fs').rmSync('dist-server', { recursive: true, force: true })\"",
     "build:server": "tsc -p server/tsconfig.json && tsc-alias -p server/tsconfig.json",
-    "postbuild:server": "node scripts/copy-computer-semantics-bin.mjs",
     "preview": "vite preview",
     "typecheck": "tsc --noEmit -p tsconfig.json && tsc --noEmit -p server/tsconfig.json",
     "lint": "eslint src/ server/",
@@ -56,7 +51,7 @@
     "start": "npm run build && npm run server",
     "release": "./release.sh",
     "prepublishOnly": "npm run build",
-    "postinstall": "node scripts/fix-node-pty.js && npm run build:semantics",
+    "postinstall": "node scripts/fix-node-pty.js",
     "prepare": "husky",
     "update:platform": "./update-platform.sh"
   },