feat(grok): add Grok Build (xAI) as a seventh CLI run mode

SessionMode gains 'grok', a first-class backend alongside Claude Code,
shell, OpenCode, Codex, Gemini, Antigravity and Pi: its own PTY, tmux
session, charcoal tab identity ('gk' badge), welcome button, run-mode
entry, cron agentType, Docker and remote-SSH command defaults, and
clone-repo Brain option. Flag surface verified live against grok 1.0.5.

Grok mixes two existing shapes and the wiring follows from that:

- Codex-shaped on permissions: the bypass switch is GrokConfig.alwaysApprove
  (--always-approve, grok's bypassPermissions mode; config-level deny rules
  still apply on top). The Run button sends it true, like runAntigravity(),
  and clampExternalCliBypassForOwner() puts grok in the only-if-sent branch:
  a bare grok spawn is grok's own ask-mode default, which is already safe,
  so only a sent config needs the flag forced off. Cron needs nothing for
  the same reason.
- OpenCode-shaped on rendering: grok is a fullscreen alternate-screen TUI
  with mouse support, so it stays OUT of isAltScreenStripMode() and lands
  on the narrow tmux-attach strip and the 'buffer' local-echo fallthrough
  (unmeasured against an authenticated composer; documented fallback is the
  'off' branch).
- Pi-shaped on resolution: 'grok' has npm squatters (@vibe-kit/grok-cli
  also installs a grok bin), so grok-cli-resolver.ts version-probes every
  candidate (grok --version, killSignal SIGKILL, VITEST-gated) and
  GET /api/grok/status surfaces path AND version; GROK_VERSION_REGEX is
  shared with the dependency registry so doctor and run mode cannot drift.

Env allowlist gains GROK_* plus the XAI_* vendor namespace (XAI_API_KEY is
grok's documented headless auth var), the same narrow-vendor reasoning as
GOOGLE_* for gemini. Resume is id-regexed on purpose: grok's own --resume
also matches session titles, which are arbitrary user strings that must
never reach the bash -c spawn line.

Docker: grok is not on npm, so the agent image installs it in its own step
(xAI's installer has no --dir override; the binary is copied to
/usr/local/bin and root's ~/.grok dropped in the same layer), and
credentials are seeded per-file (auth.json, config.toml, pager.toml; the
dir also holds sessions/, memory/ and the ~160MB binary). Remote SSH routes
through the login-shell wrapper like the other agent CLIs.

Verified end to end on an isolated CODEMAN_INSTANCE with grok 1.0.5
installed: /api/grok/status resolves and reports the probed version,
quick-start spawns a pane whose command line ends in 'grok
--always-approve', the real TUI renders (OAuth device screen on an
unauthenticated box), and grokConfig round-trips through state.json.
Docs: docs/grok-integration.md (user guide) + docs/grok-integration-plan.md
(decisions, verification record, follow-ups).

Tests: test/grok-mode.test.ts, test/grok-cli-resolver.test.ts, plus
extended clamp/system-routes/render-index-html/run-mode-ui/mobile-overview/
local-echo-gating coverage. npm test (the CI gate) green: 5910 tests.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/web/public/app.js

@@ -2243,9 +2243,11 @@ class CodemanApp {
           ? 'Antigravity'
           : mode === 'pi'
             ? 'Pi'
-            : mode === 'opencode'
-              ? 'OpenCode'
-              : 'Claude';
+            : mode === 'grok'
+              ? 'Grok'
+              : mode === 'opencode'
+                ? 'OpenCode'
+                : 'Claude';
   }
 
   async toggleResponseViewer() {
@@ -4725,7 +4727,7 @@ class CodemanApp {
           <span class="tab-status ${status}" aria-hidden="true"></span>
           <span class="tab-info">
             <span class="tab-name-row">
-              ${mode === 'shell' ? '<span class="tab-mode shell" aria-hidden="true">sh</span>' : mode === 'opencode' ? '<span class="tab-mode opencode" aria-hidden="true">oc</span>' : mode === 'codex' ? '<span class="tab-mode codex" aria-hidden="true">cx</span>' : mode === 'gemini' ? '<span class="tab-mode gemini" aria-hidden="true">gm</span>' : mode === 'antigravity' ? '<span class="tab-mode antigravity" aria-hidden="true">ag</span>' : mode === 'pi' ? '<span class="tab-mode pi" aria-hidden="true">pi</span>' : ''}
+              ${mode === 'shell' ? '<span class="tab-mode shell" aria-hidden="true">sh</span>' : mode === 'opencode' ? '<span class="tab-mode opencode" aria-hidden="true">oc</span>' : mode === 'codex' ? '<span class="tab-mode codex" aria-hidden="true">cx</span>' : mode === 'gemini' ? '<span class="tab-mode gemini" aria-hidden="true">gm</span>' : mode === 'antigravity' ? '<span class="tab-mode antigravity" aria-hidden="true">ag</span>' : mode === 'pi' ? '<span class="tab-mode pi" aria-hidden="true">pi</span>' : mode === 'grok' ? '<span class="tab-mode grok" aria-hidden="true">gk</span>' : ''}
               <span class="tab-name" data-session-id="${id}">${escapeHtml(tabLabel)}</span>
               <span class="tab-detached-badge" aria-hidden="true">detached</span>
             </span>
@@ -6154,7 +6156,9 @@ class CodemanApp {
               ? 'Kill Tmux & Antigravity'
               : session.mode === 'pi'
                 ? 'Kill Tmux & Pi'
-                : 'Kill Tmux & Claude Code';
+                : session.mode === 'grok'
+                  ? 'Kill Tmux & Grok'
+                  : 'Kill Tmux & Claude Code';
     }
 
     document.getElementById('closeConfirmModal').classList.add('active');