Allocate entity subjects and expose causal occurrence receipts

[flyingrobots]

Goal

Make dependency-pure entity capture usable by applications that do not already own an independent semantic subject, without moving causal identity or ordering policy into the application.

Contract

• Distinguish an application-supplied semantic subject from the substrate occurrence that admits it.
• Add an allocation form for entity.add that derives an opaque subject from git-warp's writer-local dot machinery.
• Return the admitted entity subject and an opaque occurrence coordinate on the WriteReceipt.
• Let the coordinate answer causal relation through version-vector context and deterministic presentation order through git-warp's canonical EventId comparator.
• Keep wall-clock observations such as capturedAt as payload metadata only.
• Preserve repeated additions of one semantic subject as distinct substrate occurrences.

Non-goals

• Enforcing distributed semantic-subject uniqueness.
• Asking applications to maintain writer counters, Lamport state, version vectors, or custom sort keys.
• Treating a version vector as a total-order clock.
• Implementing Think retrieval optics in this issue.

Acceptance

• Two auto-allocated entity writes with identical payload timestamps receive distinct subjects and occurrence ids.
• Sequential occurrences report causal order.
• Concurrent occurrences remain causally incomparable while sorting deterministically by canonical event order.
• Supplied-subject entity.add continues to work and returns a distinct occurrence for every admitted write.
• Documentation states the ownership boundary and corrects the current application-owned ordering advice.
• Focused tests, type checks, and repository gates pass.

[coderabbitai]

🔗 Related PRs

#768 - Classify v19 writes with admission outcomes [merged]

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