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>

skills/codeman/reference/verbs.md

@@ -343,7 +343,7 @@ recovered by submitting it with `{"input":"\r"}`.
 
 ⚠️ `stop` and `blocked` fire for `claude` sessions only (they are Claude Code hooks,
 and only when the workspace actually has them, see [§5.1](#51-where-to-spawn)). On
-`shell`/`opencode`/`codex`/`gemini`/`antigravity`/`pi`, requesting them explicitly is a
+`shell`/`opencode`/`codex`/`gemini`/`antigravity`/`pi`/`grok`, requesting them explicitly is a
 400, and lifecycle transitions there are coarse (a short shell command may emit **no**
 `idle` transition at all, verified live), so synchronize those with markers.
 
@@ -369,7 +369,7 @@ from the transcript file, which is flushed slightly *after* the `stop` hook fire
 single read taken the instant send-and-wait returns comes back `""` even though the
 turn finished (verified live: empty on the first call, full text seconds later). `text`
 is also `""` before the worker's first completed turn, and always `""` for modes with
-no transcript (`shell`, `opencode`, `gemini`, `antigravity`, `pi`; the first four
+no transcript (`shell`, `opencode`, `gemini`, `antigravity`, `pi`, `grok`; the first four
 verified live, pi from the same source path), which is
 why the loop above is bounded rather than open-ended. Fall back to the terminal buffer
 there, tail in **bytes** (`textOutput` in `GET .../output` stays empty for interactive
@@ -454,7 +454,7 @@ turn), and both better than diffing terminal samples:
 ```
 
 ⚠️ `active-tools` is parsed out of Claude's own output format, so it is **empty for
-`opencode`/`codex`/`gemini`/`antigravity`/`pi`** (those parsers are skipped wholesale) and
+`opencode`/`codex`/`gemini`/`antigravity`/`pi`/`grok`** (those parsers are skipped wholesale) and
 in practice empty for `shell`. Source-verified, not measured live.
 
 Only if neither helps: sample `terminal?tail=` twice a few seconds apart. A changing