refactor(mothership): a saved Stop handoff's id wins on restore

[waleedlatif1]

Summary

Follow-up to #8746, from its review. No behaviour change for anything staging can produce.

• Restoring an old saved queue, the seed's id wins. refactor(mothership): keep a queued send's reused id in one field #8746 moves the id a saved Stop handoff carried to resumeUserMessageId. Where an entry also had its own resumeUserMessageId and the two differed, it kept the entry's. It now keeps the seed's. That is the id the build that saved the entry sent: queuedSendHandoff?.userMessageId ?? resumeUserMessageId. Staging never produces two different ids, but the mapping now matches it exactly.
• resumeUserMessageId's doc comment names every path that sets it. Besides a send an unmount withdrew, these are:
  • a Send-now restored from its stored Stop handoff;
  • a dispatch put back in the queue.

Type of Change

• Improvement (refactor)

Testing

• moves the reused id a saved Stop handoff carried onto the entry, over its own (store.dom.test.ts) gains an entry carrying both ids. It fails on staging.
• The targeted suite passes 1072/1072. The quick gate (lint, typecheck, audits and unit tests) ran on the CI runner.

Checklist

• Code follows project style guidelines
• Self-reviewed my changes
• Tests added/updated and passing
• No new warnings introduced
• I confirm that I have read and agree to the terms outlined in the Contributor License Agreement (CLA)

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1 Skipped Deployment

Project	Deployment	Actions	Updated
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[waleedlatif1]

@greptile

[waleedlatif1]

@cubic-dev-ai review this PR

[cubic-dev-ai]

@cubic-dev-ai review this PR

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[cubic-dev-ai]

No issues found across 3 files

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

_{Turn on auto-fix | Re-trigger cubic}

[cubic-dev-ai]

No issues found across 3 files

Confidence score: 5/5

• Automated review surfaced no issues in the provided summaries.
• No files require special attention.

_{Turn on auto-fix | Re-trigger cubic}

[greptile-apps]

Confidence Score: 5/5

[Medium risk] Changes how a queued message picks its send ID on restore.

This PR appears safe to merge.

What we checked:

• Restore retries the wrong message: The older send path preferred the handoff’s ID. Restore now keeps that same ID, and the current send path reads it from resumeUserMessageId.

Summary

Restoring an older saved queue now prefers the Stop handoff’s message ID when the entry carries two different IDs. This matches the older send path.

• Adds a regression case with conflicting IDs.
• Expands the resumeUserMessageId comment to cover its recovery paths.
• No actionable issues found. Tests were inspected, not run.

_{Reviews (1) · Last reviewed commit: "refactor(mothership): a saved Stop hando..." · Reviewed by Greptile}