refactor(heartbeat): remove Completed section and tighten section gating

- Remove ## Completed section from HEARTBEAT.md template; completed
  tasks should be deleted, not accumulated
- Change in_active_section from tri-state (None/True/False) to bool
  (True/False) so stray text before any ## heading no longer triggers
  heartbeat
- Add test cases for stray pre-heading text and ## Notes section
- Update docs/chat-commands.md to reference ## Active Tasks

docs/chat-commands.md

@@ -56,17 +56,17 @@ Preset names come from the top-level `modelPresets` config. Switching is runtime
 
 ## Periodic Tasks
 
-The gateway wakes up every 30 minutes and checks `HEARTBEAT.md` in your workspace (`~/.nanobot/workspace/HEARTBEAT.md`). If the file has tasks, the agent executes them and delivers results to your most recently active chat channel.
+The gateway wakes up every 30 minutes and checks `HEARTBEAT.md` in your workspace (`~/.nanobot/workspace/HEARTBEAT.md`). If the file has tasks under `## Active Tasks`, the agent executes them and delivers results to your most recently active chat channel. If there are no active tasks, the heartbeat is skipped silently.
 
 **Setup:** edit `~/.nanobot/workspace/HEARTBEAT.md` (created automatically by `nanobot onboard`):
 
 ```markdown
-## Periodic Tasks
+## Active Tasks
 
 - [ ] Check weather forecast and send a summary
 - [ ] Scan inbox for urgent emails
 ```
 
-The agent can also manage this file itself — ask it to "add a periodic task" and it will update `HEARTBEAT.md` for you.
+The agent can also manage this file itself — ask it to "add a periodic task" and it will update `HEARTBEAT.md` for you. Completed tasks should be deleted from the file, not moved to another section.
 
 > **Note:** The gateway must be running (`nanobot gateway`) and you must have chatted with the bot at least once so it knows which channel to deliver to.

nanobot/cli/commands.py

@@ -107,7 +107,7 @@ _HEARTBEAT_PREAMBLE = (
 def _heartbeat_has_active_tasks(content: str) -> bool:
     """True if HEARTBEAT.md has task lines, ignoring headers, blanks and comments."""
     in_comment = False
-    in_active_section: bool | None = None
+    in_active_section: bool = False
     for line in content.splitlines():
         stripped = line.strip()
         if in_comment:

nanobot/templates/HEARTBEAT.md

@@ -5,14 +5,10 @@ This file is checked periodically by your nanobot agent.
 Register it as a cron job (e.g. `cron add --name heartbeat --schedule "every 30m" --message "Check HEARTBEAT.md"`) to get the same behavior as the legacy heartbeat service.
 
 If this file has no tasks (only headers and comments), the agent will skip it.
+Completed tasks should be deleted, not kept — heartbeat only reads "Active Tasks".
 -->
 
 ## Active Tasks
 
 <!-- Add your periodic tasks below this line -->
 
-
-## Completed
-
-<!-- Move completed tasks here or delete them -->
-

tests/cli/test_commands.py

@@ -960,8 +960,10 @@ def test_heartbeat_retains_recent_messages_by_default():
         ("<!--\nmulti-line\ncomment\n-->\n", False),  # block comment, not tasks
         ("<!-- single line -->\n", False),
         ("## Active Tasks\n\n- water the plants\n", True),
-        ("## Completed\n\n- water the plants\n", False),
         ("## Active Tasks\n\n### Garden\n\n- water the plants\n", True),
+        ("## Notes\n\nsome random note\n", False),
+        ("stray text before any heading\n## Active Tasks\n\n- task\n", True),
+        ("stray text before any heading\n", False),
     ],
 )
 def test_heartbeat_has_active_tasks(content, expected):