fix(web): restore swarm member list after page refresh

[wbxl2000]

Related Issue

No linked issue — the problem is explained below.

Problem

In the web UI, an AgentSwarm tool card loses its whole member list when the page is refreshed while subagents are still running: the card falls back to the "waiting for subtasks to join…" placeholder until the swarm's final tool result lands. Completed subagents never reappear at all.

Root cause: the card's live member rows only exist in the client's in-memory task store, populated by WS events. Only subagent.spawned carries the swarm identity metadata (parentToolCallId / swarmIndex / description), and on refresh that event is never replayed — the snapshot has no subagent roster, REST /tasks only serves the main agent's background tasks, and later subagent.* events carry just the subagentId, so the identity metadata is unrecoverable client-side.

What changed

• Server: a new SubagentRosterTracker (same volatile-state pattern as the existing InFlightTurnTracker, owned by WSBroadcastService and updated inside its per-session dispatch queue) accumulates the live subagent roster per session and drops it on turn.ended, after which the swarm's <agent_swarm_result> tool output in the wire transcript is the restore source. The roster rides the session snapshot as an optional subagents field (protocol schema extended; optional for cross-version tolerance).
• Web: the snapshot sync seeds tasksBySession from the roster (preserving any accumulated streamed output), and the taskCreated merge no longer lets a post-refresh skeleton re-projection clobber the roster-seeded description with the 'Sub Agent' placeholder. The explicit run_in_background flag now round-trips so foreground swarm members aren't misclassified as background agents.

This fits the existing refresh architecture: the snapshot is already the designated rebuild channel for volatile stream state (in_flight_turn, pending approvals/questions), and the roster is the same class of data. Older servers/clients interoperate both ways since the field is additive and optional.

Checklist

• I have read the CONTRIBUTING document.
• I have linked a related issue, or explained the problem above.
• I have added tests that prove my feature works.
• Ran gen-changesets skill, or this PR needs no changeset.
• Ran gen-docs skill, or this PR needs no doc update.

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🦋 Changeset detected

Latest commit: be0ac31

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@moonshot-ai/kimi-code	Patch

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commit: be0ac31

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[chatgpt-codex-connector]

Restrict roster clearing to the main turn

When any subagent finishes, its own turn.ended frame is published on the same session with agentId set to the subagent, and existing code already treats non-main turn frames specially (the web projector routes them as subagent progress and InFlightTurnTracker filters them out). This unconditional delete clears the whole roster as soon as the first child turn ends, so a refresh while the parent AgentSwarm call is still waiting on other subagents again loses the member list before the final swarm result is in the transcript; only the main agent's turn.ended should drop the roster.

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