derive-testslisted

# X2 Derive Tests Turn the locked portion into its tests. Nothing here is authored from imagination: the locked prototype is the acceptance contract, and the tests are projections of it. ## What derives from the lock - **The per-slice fidelity record**, derived mechanically: a deterministic exporter reads the locked artifact on disk into a computed record, and the built screens are compared against that record computationally, in both directions (everything in the record renders; nothing renders beyond it). Never hand-derive fidelity: a hand-typed summary standing in for the artifact produces drift as its designed output, because the artifact is never read again after the lock. The third project exited two slices with drifted screens that way, then built the mechanical route mid-project and drift stopped (record: PC-30). The ledger file (`design/ledger/slice-NNN.md`) keeps only what cannot be computed: acceptance scenarios and owner rulings, including licensed divergences. - **The portion is declared, never assumed.** A locked portion smaller than a whole screen is declared as excluded subtrees, each citing its ruling, held in the same extent guard as the comparison. And coverage is per drawn state, not per screen: a built state that ships never-compared is the gap an extent guard that only sees screens cannot see. - **Chrome is contract; sample content is illustration.** The locked artifact says which parts of a screen are specification and which a