Answer plain user messages in channels via a channel-anchor wake

A human message in a channel woke agents only through @mentions, DM
counterparts, or prior thread participants - and the flat composer
always sends threadId=null, so typing in #general summoned nobody and
the room stayed silent.

- Track which agents each wake path summoned in one woken set (also
  prevents latent double-wakes between the paths)
- When a non-slash human message in a channel wakes nobody, wake the
  channel's most senior active agent member with an enabled provider
  (c_suite > director > lead > staff, then hire date); they can pull
  teammates in with @mentions
- Log when a channel has no runnable agent so silence is diagnosable
- Integration test: plain #general message wakes the CEO who replies;
  an explicit mention still wakes exactly one agent

src/main/services/chat-service-internal.ts

@@ -30,6 +30,7 @@ export interface FileAttachmentRow {
 export interface SpaceRow {
   id: string;
   org_id: string;
+  name: string;
   visibility: string;
   space_type: string;
 }