add the team chat inbox over the broker

Renders broker traffic as a chat timeline and makes the user a first-class
participant. The broker grows a Stream<TeamMessage> and a recipient field,
auto-registers a virtual `user` member, and gains sendAsUser. A Flutter-free
TeamChatModel (owned by the orchestrator) accumulates the feed and exposes
postAsUser with @-routing (a new at_commands helper mirroring slash) and an
optional interrupt that cancels the target's turn before delivery. One model
backs two surfaces: a compact cockpit widget that pops out into a full
workspace chat pane. CLI parity via clide.team-chat.open / .post.

T-180.

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

CHANGELOG.md

@@ -75,6 +75,10 @@ heading, and (b) bumping `pubspec.yaml` `version:` in the same commit.
 - Fork a Claude conversation into a new pane — `/fork` (or a roster Fork
   button / `clide.agent.fork`) branches a session via `--resume … --fork-session`,
   opening an independent continuation that leaves the original untouched. (T-172, D-77)
+- Team chat inbox — broker traffic renders as a chat timeline (colour-coded
+  sender chips), in a compact cockpit widget that pops out to a full pane. The
+  user is a first-class participant: post with `@name` routing (or broadcast),
+  with an interrupt tickbox that cancels the target's turn before delivery. (T-180, D-77)
 - Team coordination broker (T-170, D-77) — clide hosts an in-process MCP
   server (`clide-team`) for managed sessions over the stream-json control
   channel, giving agents tools to message each other, broadcast, see the