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

main.py

@@ -214,6 +214,15 @@ def ai_handler(msg: IncomingMessage) -> str:
     if cmd in ("sessions",):
         return _format_sessions()
 
+    # Reset session for this conversation
+    if cmd in ("new", "reset"):
+        cleared = _runtime.reset_session(msg.conversation_id)
+        if _hook_mgr:
+            _hook_mgr.trigger(HookEvent(type="command", action="new"))
+        if cleared:
+            return "🆕 Session cleared — next message starts a fresh conversation."
+        return "🆕 No active session to clear — already starting fresh."
+
     # Cron management commands
     if cmd.startswith("cron"):
         return _handle_cron_command(cmd)
@@ -1606,6 +1615,7 @@ def _format_help() -> str:
         "• `help` — This help message\n"
         "• `time` — Server time\n"
         "• `sessions` — Active session count\n"
+        "• `new` / `reset` — Start a fresh conversation (clears session)\n"
         "• `reload` — Reload config and skills\n"
         "\n"
         "*Runtime:*\n"