refactor(heartbeat): config-driven checks, channel delivery, remove hardcoded values

Heartbeat system overhaul:
- Fix email/calendar checks to parse JSON output correctly
- Add per-check cooldowns and quiet hours config
- Send findings to Discord channel instead of just logging
- Auto-reindex KB when stale files detected
- Claude CLI called only if HEARTBEAT.md has extra instructions
- All settings configurable via config.json heartbeat section

Move hardcoded values to config.json:
- allowed_tools list (claude_session.py)
- Ollama URL/model (memory_search.py now reads ollama.url from config)

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/main.py

@@ -87,12 +87,15 @@ def main():
         from src.heartbeat import run_heartbeat
 
         interval_min = hb_config.get("interval_minutes", 30)
+        hb_channel = hb_config.get("channel", "echo-core")
 
         async def _heartbeat_tick() -> None:
-            """Run heartbeat and log result."""
+            """Run heartbeat and send findings to channel."""
             try:
-                result = await asyncio.to_thread(run_heartbeat)
+                result = await asyncio.to_thread(run_heartbeat, config)
                 logger.info("Heartbeat: %s", result)
+                if result != "HEARTBEAT_OK":
+                    await _send_to_channel(hb_channel, result)
             except Exception as exc:
                 logger.error("Heartbeat failed: %s", exc)
 
@@ -105,7 +108,8 @@ def main():
             max_instances=1,
         )
         logger.info(
-            "Heartbeat registered (every %d min)", interval_min
+            "Heartbeat registered (every %d min, channel: %s)",
+            interval_min, hb_channel,
         )
 
     # Telegram bot (optional — only if telegram_token exists)