Add main-loop enable/disable per-agent toggle

- self_main_loop.py: 'enabled' map in config (default all True);
  do_check skips disabled agents (marks disabled:true in results);
  new enable/disable actions with optional --agent.
- box-ctl.py: main-loop enable|disable [--agent <name>] actions,
  USAGE updated.

Check skips disabled agents so the loop can be toggled per
Chromebox without stopping the systemd timer.

Session: sidechat/chromebox-ops

bin/self_main_loop.py

@@ -93,11 +93,16 @@ def get_config(st):
     agents = [a for a in agents if a in DEFAULT_AGENTS]
     prompt = dict(DEFAULT_PROMPT_SIDECHAT)
     prompt.update(cfg.get("prompt_sidechat") or {})
+    enabled = dict(cfg.get("enabled") or {})
+    # Default any unlisted agent to enabled.
+    for a in agents:
+        enabled.setdefault(a, True)
     return {
         "agents": agents or list(DEFAULT_AGENTS),
         "prompt_sidechat": prompt,
         "sender": cfg.get("sender") or DEFAULT_SENDER,
         "read_limit": int(cfg.get("read_limit") or READ_LIMIT),
+        "enabled": enabled,
     }
 
 
@@ -180,11 +185,15 @@ def do_check(only_agent=None):
         return {"ok": False, "error": "unknown agent: %s" % only_agent}
 
     agents_state = st.get("agents") or {}
+    enabled = cfg.get("enabled") or {}
     results = {}
     prompted = 0
     errors = 0
 
     for agent in agents:
+        if not enabled.get(agent, True):
+            results[agent] = {"ok": True, "new": 0, "disabled": True}
+            continue
         wm = agents_state.get(agent) or {}
         ok, payload = read_main_chat(agent, cfg["read_limit"])
         if not ok:
@@ -231,19 +240,40 @@ def do_check(only_agent=None):
         st["config"] = {"agents": cfg["agents"],
                         "prompt_sidechat": cfg["prompt_sidechat"],
                         "sender": cfg["sender"],
-                        "read_limit": cfg["read_limit"]}
+                        "read_limit": cfg["read_limit"],
+                        "enabled": dict(cfg.get("enabled") or
+                                        {a: True for a in cfg["agents"]})}
     save_state(st)
     return {"ok": errors == 0, "prompted": prompted, "errors": errors,
             "new_total": sum(r.get("new", 0) for r in results.values()),
             "agents": results}
 
 
+def _set_enabled(agent, value):
+    """Enable/disable the loop for one agent (or all if agent is None)."""
+    st = load_state()
+    cfg = st.get("config") or {}
+    agents = cfg.get("agents") or list(DEFAULT_AGENTS)
+    agents = [a for a in agents if a in DEFAULT_AGENTS] or list(DEFAULT_AGENTS)
+    if agent and agent not in DEFAULT_AGENTS:
+        return {"ok": False, "error": "unknown agent: %s" % agent}
+    enabled = dict(cfg.get("enabled") or {})
+    targets = [agent] if agent else agents
+    for a in targets:
+        enabled[a] = value
+    cfg["enabled"] = enabled
+    st["config"] = cfg
+    save_state(st)
+    return {"ok": True, "enabled": {a: enabled.get(a, True) for a in targets}}
+
+
 def do_status():
     st = load_state()
     cfg = get_config(st)
     agents_state = st.get("agents") or {}
     return {"ok": True,
             "config": cfg,
+            "enabled": cfg.get("enabled") or {},
             "watermark": agents_state,
             "last_run": st.get("last_run"),
             "last_result": st.get("last_result")}
@@ -261,8 +291,16 @@ def main(argv):
         print(json.dumps(do_status()))
         return 0
 
+    if action == "enable":
+        print(json.dumps(_set_enabled(only_agent, True)))
+        return 0
+
+    if action == "disable":
+        print(json.dumps(_set_enabled(only_agent, False)))
+        return 0
+
     if action != "check":
-        print(json.dumps({"ok": False, "error": "usage: check|status [--agent X]"}))
+        print(json.dumps({"ok": False, "error": "usage: check|status|enable|disable [--agent X]"}))
         return 2
 
     # Overlap guard: timer may fire while a slow run is still going.