Fix delayed sub-agent WebSocket operations

[ben-reitz]

Stacked on #2027. Fixes #2055.

Why

A sub-agent's virtual WebSocket Connection lives longer than the Workers RPC bridge used to forward one browser frame. Delayed work could therefore call connection.send() through a bridge that had already been disposed.

Think exposed this when STREAM_PENDING arrived but the later STREAM_RESUMING send was dropped, leaving the client waiting for its 60-second timeout. #2027 fixes which bridge an in-flight callable reply uses; this PR handles connection activity after that frame has finished.

What changed

• Track the live bridge for each forwarded invocation and invalidate it when the invocation ends.
• Route delayed send, setState, and close calls through the durable root Agent, in call order, with failures reported.
• Preserve the upstream broadcast capability for active nested frames and use the root when a relay has no live bridge.
• Add real WebSocket regressions for delayed delivery, state, close, ordering, failure recovery, and fresh-context broadcasts.

Validation

• pnpm run check
• Agents tests: 2,488 passed
• Reporter's Think reproduction passes in direct and sub-agent modes with STREAM_PENDING → STREAM_RESUMING → done

---

[changeset-bot]

🦋 Changeset detected

Latest commit: 1760fcf

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 2 packages

Name	Type
agents	Patch
@cloudflare/agent-think	Patch

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@cloudflare/ai-chat

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@cloudflare/channels

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@cloudflare/codemode

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hono-agents

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@cloudflare/shell

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@cloudflare/think

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@cloudflare/voice

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@cloudflare/worker-bundler

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commit: 1760fcf