fix(ble): properly remove cancelled pending detaches

When _process_pending_detaches() finds that an address has reconnected
during the grace period, the pending detach entry was not being removed
from _pending_detach dict. This caused the entry to be re-evaluated on
every cleanup cycle.

Now properly deletes the entry when cancelling the detach.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/ble_reticulum/BLEInterface.py

@@ -785,6 +785,7 @@ class BLEInterface(Interface):
 
                 if has_connected_address:
                     # New connection arrived during grace period - cancel detach
+                    del self._pending_detach[identity_hash]
                     RNS.log(f"{self} cancelled detach for {identity_hash[:8]} - address reconnected during grace period", RNS.LOG_DEBUG)
                 else:
                     # No connections - safe to detach