P4-T4: registry + bridge integration (L0 transfer invariant)

[thebeastagi]

Part of #10.

Goal: integration through the Phase-1 registry at CORE tier + bridge check: transferring the Kepler candidate into a synthetic domain enters at L0 (invariant re-verified against a real adapter); domain validators stay behind the adapter (kernel sees only evidence contracts).

Accept: registry test proves tier enforcement; bridge test proves L0 reset; dependency-rule test still passes (core never imports adapters).