Skill: CairnStone project handoff

Use this skill after a material shared-state change so the next agent can resume from canonical evidence instead of prose archaeology.

1. Verify the completed slice and record exact immutable commits, deployment runs, live versions, accepted path HEADs, and known caveats.
2. Create a compact completion/START HERE stone on the canonical project-memory chain with a stable path and structured metadata for slice, status, and next slice.
3. Link that continuation point to the important implementation, acceptance, guide, or evidence stones so the graph is navigable.
4. Move the project-memory chain HEAD only after the new continuation state is complete.
5. Send AC1 correspondence to known collaborating agent IDs after materially changing shared state. Correspondence communicates state but grants no execution authority.
6. In the handoff, point to canonical chains/hashes rather than copying large source bodies.

The next session should be able to resume deterministically from the new HEAD and path HEADs.