feat: openclaw-style secrets (env.vars + \) and per-task model routing

- Replace python-dotenv with config.json env.vars block + \ substitution
- Add models section for per-task model routing (heartbeat, subagent, default)
- Heartbeat/subagent tasks can use different models/providers than main chat
- Remove python-dotenv from dependencies
- Update all docs to reflect new config approach
- Reorganize docs into project/ and research/ subdirectories

scheduler/scheduler.py

@@ -220,6 +220,17 @@ class Scheduler:
         """List only recurring cron jobs."""
         return self._store.list_recurring()
 
+    def remove_by_channel_type(self, channel_type: str) -> int:
+        """Remove all jobs with the given channel_type. Returns count removed."""
+        ids = self._store.remove_by_channel_type(channel_type)
+        for job_id in ids:
+            for prefix in ("once-", "cron-"):
+                try:
+                    self._scheduler.remove_job(f"{prefix}{job_id}")
+                except Exception:
+                    pass
+        return len(ids)
+
     # -------------------------------------------------------------------
     # Internal
     # -------------------------------------------------------------------