Pointer Rotation Example + CI Trailer Gate

[flyingrobots]

Title
Pointer Rotation Example + CI Trailer Gate

Goal
Document rotation (re‑encrypt + update pointer) and enforce trailer when rotations occur.

Acceptance Criteria

• Example JSON pointer rotation event.
• Projection commits that include rotations add trailer: Privacy-Pointer-Rotations: <n>.
• CI check rejects projection commits with rotations that omit the trailer.

Notes

• Reference: ADR‑0004 rotation section; SPEC pointer rotation.