Build Unity action player and embodied AR evidence bridge

[BigBirdReturns]

Superseded without merge by the final authority split:

World PR #203
  owns the qualified Unity/Quest receiver, C# mirror, presentation, input, safety, launcher, build, and exact Arc return path

axm-embodied PR #15
  owns physical observation, immutable spool ingestion, journal continuity, and Genesis-facing evidence custody

Arc PR #175
  owns action law, profile/spec compilation, accepted receipts, and the offline Forge

This earlier draft uses a separate TCP sidecar and duplicates Unity receiver ownership inside axm-embodied. The accepted closure instead uses World’s file-local, offline-capable receiver and provisional candidate path, then hands only physical evidence to axm-embodied. Keeping both would create two receiver architectures and an ambiguous integration target.

No source from this PR is accepted by closure unless explicitly reconstructed over PR #203 or PR #15 in response to a demonstrated failure. World issue #204 is the sole remaining Unity/Windows/Quest/physical acceptance path.