Attract sequence, credits, demo death, and one-player flow

[StarshipSuperjam]

Parent capability: cabinet.
Delivery slice: 17. Milestone: Cabinet.
Roadmap state: provisional. Executable now: no.

Atomic obligations

• CAB-01.attract
• CAB-02.one-player

Blockers

• None
• Required delivery slices: slice 2, slice 4, slice 6, slice 8
• docs/spec/cabinet-flow.md must be settled before this leaf may close.

Completion evidence

• Proof level: playable.
• Mechanics records/catalog rows: CAB-01, CAB-02.
• Automated evidence must add roadmap-evidence: ID success and roadmap-evidence: ID failure markers for every obligation ID, attached to tests that exercise those paths.
• A gameplay-affecting PR stays draft until the operator approves the playable .sb3 at its tested commit.

Closure rule

This leaf closes only when all obligations above are delivered, every blocker is closed (or closes in the same PR), the required evidence is present, and the repository closure check passes.