Two related fixes to the Discord gateway adapter:
1. Channel name matching (free-response, allowed, ignored, no-thread channels)
Previously these config values only matched against numeric channel IDs.
If a user configured free_response_channels: cypher (by name), the adapter
would silently ignore it because it only intersected against channel_ids.
Now the adapter builds a channel_keys set that includes the channel ID,
channel name, and #channel-name form, and checks all three for each gate.
2. Flush pending text-batch tasks before shutdown
The Discord adapter uses _pending_text_batch_tasks (its own dict) for
merging rapid successive message chunks. These tasks were NOT added to
self._background_tasks (the base class list), so the base
cancel_background_tasks() never awaited them on restart/shutdown.
This caused a race: in-flight response deliveries were cancelled before
Discord had a chance to send them, resulting in silent dropped messages
visible to users as tool-log-only replies with no text body.
Fix: override cancel_background_tasks() in DiscordAdapter to await all
pending text-batch tasks (8s deadline) before delegating to the base class.
cb9308f0a6