Deleting a thread, channel, or message was a no-op/soft-delete: messages
were only dropped from the plugin outbox (still in hermes' session store,
hence searchable/recoverable) and channels/threads were merely archived.
Now deletion is complete and non-recoverable, with no search trace:
- purge.py (new): hard-delete from hermes' session store (state.db).
delete_lane wipes a channel's/thread's sessions + messages; deleting a
messages row also drops it from the FTS5 index via the delete triggers.
delete_message removes one message, matched by (session, role, exact
content, closest timestamp) since plugin m_<hex> ids aren't persisted.
- channels.py: delete() hard-deletes the row (and a channel's child
threads) instead of archiving.
- outbox.py: add delete_lane() (wipe all frames for a lane) and
message_info() (read a message's final role/text/ts for the match).
- adapter.py: on_channel_delete wipes outbox + session store;
on_message_delete purges the session-store row per message.
- App: delete confirmations no longer claim history stays for search;
ChannelStore removes a channel's threads on channel delete.
- Docs updated to describe hard deletion.
ARIA