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

heartbeat/heartbeat.py

@@ -62,6 +62,11 @@ class HeartbeatRunner:
         if not self._config.enabled:
             return 0
 
+        # Clear previous heartbeat jobs to avoid duplicates on restart
+        removed = self._scheduler.remove_by_channel_type("heartbeat")
+        if removed:
+            logger.info(f"Heartbeat: cleared {removed} stale job(s) from previous run")
+
         self._ensure_heartbeat_file()
         tasks = self._parse_heartbeat_md()
 

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
     # -------------------------------------------------------------------

scheduler/store.py

@@ -147,6 +147,22 @@ class JobStore:
             conn.commit()
             return cursor.rowcount
 
+    def remove_by_channel_type(self, channel_type: str) -> list[str]:
+        """Remove all jobs with the given channel_type. Returns removed IDs."""
+        with self._conn() as conn:
+            rows = conn.execute(
+                "SELECT id FROM jobs WHERE channel_type = ?", (channel_type,)
+            ).fetchall()
+            ids = [row["id"] for row in rows]
+            if ids:
+                conn.execute(
+                    "DELETE FROM jobs WHERE channel_type = ?", (channel_type,)
+                )
+                conn.commit()
+        if ids:
+            logger.info(f"Removed {len(ids)} jobs with channel_type={channel_type}")
+        return ids
+
     @staticmethod
     def _row_to_job(row: sqlite3.Row) -> ScheduledJob:
         return ScheduledJob(