feat(terminal): refactor runtime and add mobile workspace (#2280)

Replace the legacy terminal flow with a shared authenticated WebSocket
runtime used across web, desktop, relay, and mobile surfaces.

- introduce the v3 terminal protocol with scoped attachments, snapshots,
  ordered output, bounded replay history, reconnects, and explicit lifecycle
- harden PTY creation, restart, resize, close, force-kill, idle cleanup,
  shell selection, login mode, environment sanitization, and appearance sync
- add runtime-aware terminal APIs with relay authentication and Electron parity
- add a fullscreen mobile terminal workspace with touch scrolling,
  long-press selection, safe-area controls, quick keys, and Ctrl/Alt input
- add terminal selection attachments, preview detection, project actions,
  shell settings, and localized UI
- harden Ghostty rendering, resize recovery, Unicode handling, block
  characters, line height, and stale-row behavior
- remove the obsolete terminal SSE path and update reverse-proxy guidance
- expand terminal runtime, transport, input, selection, and store coverage
- avoid duplicate web builds when preparing mobile assets in root CI builds

packages/vscode/webview/api/index.ts

@@ -9,13 +9,20 @@ import { createVSCodeActionsAPI } from './vscode';
 import { createVSCodeGitHubAPI } from './github';
 import { createVSCodeNotificationsAPI } from './notifications';
 
-// Stub APIs return sensible defaults instead of throwing
+const terminalUnsupported = async (): Promise<never> => {
+  throw new Error('Terminal is not supported in the VS Code runtime');
+};
+
 const createStubTerminalAPI = (): TerminalAPI => ({
-  createSession: async () => ({ sessionId: '', cols: 80, rows: 24 }),
-  connect: () => ({ close: () => {} }),
-  sendInput: async () => {},
-  resize: async () => {},
-  close: async () => {},
+  listShells: terminalUnsupported,
+  createSession: terminalUnsupported,
+  connect: (_sessionId, handlers) => {
+    handlers.onError?.(new Error('Terminal is not supported in the VS Code runtime'), true);
+    return { close: () => {} };
+  },
+  sendInput: terminalUnsupported,
+  resize: terminalUnsupported,
+  close: terminalUnsupported,
 });
 
 export const createVSCodeAPIs = (): RuntimeAPIs => ({