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/web/server/lib/opencode/env-runtime.test.js

@@ -118,6 +118,19 @@ const createRuntime = (settings, options = {}) => {
 };
 
 describe('OpenCode env runtime', () => {
+  it('searches an explicit PATH without mutating the process environment', () => {
+    const defaultDir = createTempDir('openchamber-default-path-');
+    const explicitDir = createTempDir('openchamber-explicit-path-');
+    const binary = path.join(explicitDir, process.platform === 'win32' ? 'custom-shell.exe' : 'custom-shell');
+    fs.writeFileSync(binary, '#!/bin/sh\nexit 0\n');
+    if (process.platform !== 'win32') fs.chmodSync(binary, 0o755);
+    process.env.PATH = defaultDir;
+    const { runtime } = createRuntime({});
+
+    expect(runtime.searchPathFor('custom-shell', explicitDir)).toBe(binary);
+    expect(process.env.PATH).toBe(defaultDir);
+  });
+
   it('throws a specific error for a missing configured OpenCode binary in strict mode', async () => {
     const { runtime } = createRuntime({ opencodeBinary: '/missing/opencode' });