feat(grok): route interactive intake/secretary to opencode-serve images

Wire the GROK interactive path the in-place way (matching how the interactive
roles already choose ANTHROPIC_* per route), so a GROK route launches the
Grok-native opencode-serve image instead of the Claude SDK-driver image:

- _spawn_intake_container / _spawn_secretary_container pick the
  grok-prompter / grok-secretary image (ensuring the base→grok→interactive
  build chain) when the route is GROK, and stamp provider_type on the spec +
  AgentConfig so finalize routes usage to the opencode store.
- _build_intake_run_cmd / _build_secretary_run_cmd inject OPENAI_* + the
  opencode store mount + system-prompt env for GROK via a shared
  _append_interactive_provider_env, keeping ANTHROPIC_* for every other
  provider. The intake's minimal mounts (no gateway MCP) are preserved, so
  Grok intake matches the Claude intake's tool surface (the spec).
- Add a per-agent opencode store mount to the interactive host paths so
  interactive Grok usage/cost is captured like the one-shot path.

Removes the interim Phase-0 routing guard (the real path supersedes it) and
retires the unused AgentProvider.spawn_interactive/InteractiveSpawnSpec seam —
the interactive roles have a bespoke assembly that the one-shot provider
surface doesn't fit, so the fork lives in their own builders.

UNVERIFIED-LIVE: end-to-end intake/secretary chat on Grok needs the stack up +
opencode serve confirmed against grok-build-0.1.

pyproject.toml

@@ -170,8 +170,6 @@ select = [
 # signature for keyword-argument compatibility (mypy override check), but the
 # stub bodies are empty — ARG002 would require renaming them, which breaks mypy.
 "tests/unit/services/test_optimal_grounding.py" = ["ARG002"]
-# Minimal AgentProvider stub exercising the interactive default — same reason.
-"tests/unit/llm/test_provider_base.py" = ["ARG002"]
 
 # =============================================================================
 # MyPy Configuration