Consider optional Actor revision preconditions for SuspendActor and CreateTag #2551

Proposal

Consider optional source-Actor revision preconditions for SuspendActor and CreateTag. This is an API extension, not a change to the current default semantics: an ordinary CreateTag captures the snapshot the Actor holds when the call executes.

An optional UID and revision would let a client ask to capture or copy exactly the Actor revision it observed. A mismatch should be rejected under the Actor lease before a checkpoint starts or a tag is reserved. Clients that omit the condition should retain the current behavior.

The narrowed implementation in #2543 uses internal workflow parameters for this purpose. Public request fields are not needed to complete #2533 and should receive separate API review.

Decisions and validation

• Choose the public shape of the precondition and the conflict/retry contract.
• Cover stale UID after delete/recreate, stale revision after pause/resume or template update, and a changed snapshot between suspend and tag.
• Prove a rejected request does not capture, reserve a tag, or copy data; cover the unchanged no-precondition path.

AI assistance: Codex helped draft this proposal.