TT1: Merge semantics for admitted stream facts across worldlines #245
Description
From docs/spec-time-streams-and-wormholes.md: clarify merge semantics for stream-derived observation facts when clients buffer "future" events and later fork/merge/resync.
Scope:
- Define whether previously-buffered stream events admitted into a forked branch remain valid on merge, and under what authority/policy.
- Define how StreamAdmissionDecision records participate in merge conflicts.
- Define any "paradox quarantine" rules at the stream/fact layer.
Acceptance:
- Spec defines deterministic merge behavior (including what is forbidden) and how tools surface it.