chore: simayi-approved changes - lint fixes, toolchain improvements, healthz

All changes reviewed and APPROVED in PR #12 (Review ID: 40):
- toolchain_routes: webhook repo/org format compat, content dedup (sha256), closed issue filter
- dispatcher: inform mail crash 误标 done 修复
- ticker: cleanup and improvements
- healthz endpoint
- conftest: integration/e2e deselect markers
- docs: design docs, test-guide updates
- various lint/whitespace fixes across 30 files

src/daemon/counter.py

@@ -73,7 +73,7 @@ class ActiveAgentCounter:
         cd = seconds if seconds is not None else self._default_cooldown_seconds
         self._cooldown_until[agent_id] = time.time() + cd
         logger.info("Cooldown set for %s: %.0fs (until %.0f)",
-                    agent_id, cd, self._cooldown_until[agent_id])
+                     agent_id, cd, self._cooldown_until[agent_id])
 
     async def can_acquire(self, agent_id: str, session_id: str = "main") -> bool:
         """三层检查：cooldown → global → per agent → per session key"""