fix(app): keep agent details and stay quiet after a current timeline answer

The timeline fetch that a current answer skips also delivered the full agent
row, and the replica cache stores only part of it. After a cold reload with
an empty incremental directory page, usage, modes, permissions and runtime
info stayed empty. The subscribe answer now carries the row for each current
chat, gated with the rest of the freshness check.

The panel also reported ready before the timeline owner was published, so a
connected render with cached content showed Updating messages. No owner now
reads as a check that has not begun.

packages/protocol/src/messages.ts

@@ -5259,6 +5259,9 @@ export const SetAgentTimelineSubscriptionResponseMessageSchema = z.object({
     requestId: z.string(),
     // COMPAT(timelineFreshnessCheck): added after v0.15.3, remove after 2027-05-09.
     timelines: z.record(z.string(), TimelineFreshnessSchema).optional(),
+    // The agent row for each chat answered "current", which gets no timeline fetch to carry it.
+    // COMPAT(timelineFreshnessCheck): added after v0.15.3, remove after 2027-05-09.
+    agents: z.record(z.string(), AgentSnapshotPayloadSchema).optional(),
   }),
 });