Harden spawned actor source persistence

[davidkpiano]

Summary:

• add typed enq.spawn("worker", options) for registered actor sources while retaining logic-value spawning
• resolve string sources immediately and persist the exact authored key; duplicate keys may share logic and later diverge through provide, extend, or migration
• propagate actor-map typing so required input and returned event/snapshot/output types come from the selected source; unknown registered keys are type errors
• keep logic-value reverse lookup as convenience, using the first matching key, and keep unregistered inline children non-persistable
• preserve actor refs and children[id] as the communication model; no family or descriptor abstraction
• document persistence/failure behavior and cover runtime, types, provide/extend, migration, and durable descriptors

Verification:

• pnpm test:core (2,326 passed; 32 skipped; 3 todo)
• pnpm typecheck
• pnpm lint
• pnpm format:check
• pnpm build
• production bundle smoke test

[changeset-bot]

🦋 Changeset detected

Latest commit: 23e2567

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

This PR includes changesets to release 1 package

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xstate	Patch

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[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no bugs or issues to report.