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/index.html

@@ -430,6 +430,10 @@
               <svg width="20" height="20" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><polygon points="5 3 19 12 5 21 5 3"/></svg>
               Run Pi
             </button>
+            <button class="welcome-btn welcome-btn-grok" id="welcomeGrokBtn" style="display: none;" onclick="app.setRunMode('grok'); app.runGrok()">
+              <svg width="20" height="20" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><polygon points="5 3 19 12 5 21 5 3"/></svg>
+              Run Grok
+            </button>
           </div>
           <div class="welcome-qr" id="welcomeQr" onclick="app.toggleWelcomeQrSize()">
             <div class="welcome-qr-inner" id="welcomeQrInner"></div>
@@ -607,6 +611,9 @@
               <button class="run-mode-option" data-mode="pi" onclick="app.setRunMode('pi')">
                 <span class="run-mode-dot pi"></span>Pi
               </button>
+              <button class="run-mode-option" data-mode="grok" onclick="app.setRunMode('grok')">
+                <span class="run-mode-dot grok"></span>Grok
+              </button>
               <div class="run-mode-sep"></div>
               <button class="run-mode-option" data-mode="shell" onclick="app.setRunMode('shell')">
                 <span class="run-mode-dot shell"></span>Terminal / Shell
@@ -884,6 +891,7 @@
                 <option value="gemini">Gemini</option>
                 <option value="antigravity">Antigravity</option>
                 <option value="pi">Pi</option>
+                <option value="grok">Grok</option>
               </select>
             </div>
             <div class="form-row"><label>Working Directory</label><input type="text" id="schWorkingDir" placeholder="/absolute/path"></div>
@@ -2616,6 +2624,7 @@
                 <option value="opencode" data-cli="opencode">OpenCode</option>
                 <option value="antigravity" data-cli="antigravity">Antigravity</option>
                 <option value="pi" data-cli="pi">Pi</option>
+                <option value="grok" data-cli="grok">Grok</option>
                 <option value="shell">Shell (no agent)</option>
               </select>
               <span class="form-hint">Which CLI to point the Run button at once the clone finishes. Changeable any time from the Run dropdown.</span>
@@ -2756,7 +2765,7 @@
             <div class="form-row">
               <label>Image</label>
               <input type="text" id="dockerImage" placeholder="codeman/agent:base" autocomplete="off" autocapitalize="off" spellcheck="false">
-              <span class="form-hint">Build it once with <code>node scripts/build-agent-image.mjs</code>. Contains node + claude/codex/gemini/opencode/agy/pi + tmux.</span>
+              <span class="form-hint">Build it once with <code>node scripts/build-agent-image.mjs</code>. Contains node + claude/codex/gemini/opencode/agy/pi/grok + tmux.</span>
             </div>
             <div class="form-row">
               <label>Network</label>