fix: drop state_transition_history field — removed in a2a-sdk 1.x

a2a-sdk 1.x's AgentCapabilities only exposes 4 fields:
streaming, push_notifications, extensions, extended_agent_card.
The state_transition_history field was removed in the v1 protobuf
schema. main.py still passed it as a kwarg, so every workspace
that reached the AgentCard construction step (line 188) crashed:

  ValueError: Protocol message AgentCapabilities has no
  "state_transition_history" field

Symptom: every claude-code + hermes workspace stuck in `provisioning`
forever — caught when the user provisioned a Design Director crew
manually via the canvas while harness 5 was running.

Why every prior smoke gate missed it:
- runtime-pin-compat.yml smokes `from molecule_runtime.main import
  main_sync` — only imports the module. AgentCapabilities() runs
  inside `async def main()`, not at module load.
- Template image boot smoke does `import every /app/*.py` — same
  story. main.py imports fine; the field error only fires at call.

The fix is one line — drop the kwarg. Fields we actually need
(streaming + push_notifications) are still passed.

Follow-up worth filing: smoke step that instantiates Adapter() +
calls a no-op setup() against a stub config. That would have
caught this before publish.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

workspace/main.py

@@ -188,7 +188,6 @@ async def main():  # pragma: no cover
         capabilities=AgentCapabilities(
             streaming=config.a2a.streaming,
             push_notifications=config.a2a.push_notifications,
-            state_transition_history=True,
         ),
         skills=[
             AgentSkill(