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>

electron/preload.cjs

@@ -44,10 +44,7 @@ if (window.location.protocol === 'file:') {
     refreshActiveTab: () => ipcRenderer.invoke('cloudcli-desktop:reload-active-tab'),
     showEnvironmentPicker: () => ipcRenderer.invoke('cloudcli-desktop:show-environment-picker'),
     showLauncher: () => ipcRenderer.invoke('cloudcli-desktop:show-launcher'),
-    showComputerAccess: () => ipcRenderer.invoke('cloudcli-desktop:show-computer-access'),
     showLocalSettings: () => ipcRenderer.invoke('cloudcli-desktop:show-local-settings'),
-    updateComputerUse: (settings) => ipcRenderer.invoke('cloudcli-desktop:update-computer-use', settings),
-    requestComputerUsePermission: (permission) => ipcRenderer.invoke('cloudcli-desktop:request-computer-use-permission', permission),
     showDesktopSettings: () => ipcRenderer.invoke('cloudcli-desktop:show-desktop-settings'),
     closeSettingsWindow: () => ipcRenderer.invoke('cloudcli-desktop:close-settings-window'),
     showActiveEnvironmentActionsMenu: () => ipcRenderer.invoke('cloudcli-desktop:show-active-environment-actions-menu'),