Onboard bar after independent review and registry migration

[Xuepoo]

Priority: P1 | Area: area:plugins | Labels: feat,P1,area:plugins | Milestone: v0.1.0 | RFC: ADR-0014 | Task: CTX-0031 | Plan: W-122

Summary: Complete independent bar review and resolve the existing registry-pins migration decision before onboarding bar. This task is separate from Beacon.

Depends on: W-40 and W-51.

Acceptance:

• Review is recorded.
• Dirty registry state is resolved by owner decision.
• Official onboarding policy is satisfied.
• Manifest hash and source pin are verified.
• No unrelated plugin pointers are changed.

Handoff: bitty-docs/docs/handoff/2026-10-02-small-core-refactor.md

[Xuepoo]

Bar onboarded via PR #70 (merged 3704f10): registry entry + submodule wiring + sdk pin d915535, independent APPROVE, CI green.