fix(grok): address adversarial-review findings across the grok-CLI conversion

A 7-dimension adversarial review (find -> independently refute) surfaced 14 real
issues; fixed each:

Runtime bugs
- GrokCliSession.send drained stdout fully BEFORE stderr — a >64KB stderr burst
  would deadlock the turn forever (spinner never clears). Drain stderr
  concurrently, and add a per-turn watchdog (ROBOCO_GROK_TURN_TIMEOUT_SECONDS,
  default 600s) that kills a wedged process and emits error+turn_end.
- Crash-restarted grok agents launched `grok -p ""` (empty prompt) — Claude gets
  a scan-for-work fallback. Default the prompt in _spawn_container so every
  dedicated provider gets it too.
- _grok_usage_json read /data/grok-usage unconditionally while its writers branch
  compose-vs-local, so a local-mode agent finalized at $0 and the cost-cap was
  inert. Single-source the path in a new _grok_usage_dir helper (read == write).
- GrokCliSession secretary role fell through to "unknown" (get_agent_role returns
  a truthy sentinel, never None), defeating the ROBOCO_AGENT_ROLE fallback.

Parity / hardening
- --deny set was missing `git tag -d` / `git reflog delete` that the Claude
  bash-guard blocks — added them (the "same set" claim is now true).
- Interactive mains now install the bash-guard hook too (defense-in-depth).
- Compose: collapse the GROK_AUTH_DIR / ROBOCO_HOST_GROK_DIR auth-mount pair into
  one canonical var so a partial override can't silently break agent auth.

Docs / comments
- Panel routing card + architecture security doc no longer say Grok runs on the
  deleted opencode runtime; orchestrator comments point at the renamed entrypoint.

Tests
- Cover the interactive _render_grok_config MCP wiring (ModuleNotFound guard +
  secretary HMAC env), the cost-cap kill-failure + interactive relay-close paths,
  the local-mode usage read, the role fallback, the turn timeout, and the new
  git denies. (#13 — a separate grok "Write" tool — investigated: grok's only
  built-in file-mutation tool is search_replace, already removed; no gap.)

Gate green: ruff, mypy, xenon, tests.

docker-compose.registry.yml

@@ -243,7 +243,7 @@ services:
       # SuperGrok auth — mount host ~/.grok at the SAME host path the orchestrator
       # hands each Grok agent's `-v`, so its auth.json exists() check passes here
       # AND the agent bind resolves on the host. `grok login` on the host. RO.
-      - ${GROK_AUTH_DIR:-${HOME}/.grok}:${ROBOCO_HOST_GROK_DIR:-${HOME}/.grok}:ro
+      - ${ROBOCO_HOST_GROK_DIR:-${HOME}/.grok}:${ROBOCO_HOST_GROK_DIR:-${HOME}/.grok}:ro
       - ${ROBOCO_DATA_DIR:-./data}/mcp-configs:/app/mcp-configs
       - ${ROBOCO_DATA_DIR:-./data}/prompts-generated:/app/prompts-generated
       - ${ROBOCO_DATA_DIR:-./data}/agent-settings:/app/agent-settings