feat(studio): link edit rechecks to script fingerprints

[w1ne]

Summary

• add deterministic Studio script fingerprints for approved staged edit code
• require matching validity fingerprints before updating pending approved ledger entries
• publish validity with the current workbench code fingerprint from useRecomputeResult

Reliability notes

• missing or mismatched validity fingerprints leave approved entries pending
• same ValidatorResult reference can update ledger evidence without rotating previous/current validity
• fingerprint stores line-normalized script length plus two independent 32-bit hashes, not full source text

Test Plan

• npm test -- --run src/studio/tests/shellStore.test.ts src/studio/tests/StagedEditSlot.test.tsx src/studio/tests/useRecomputeResult.test.tsx
• npm run typecheck
• git diff --check
• npm run build:studio
• npm run lint (passes with existing unused-disable warnings outside this slice)

Private docs: w1ne/kernelCAD-private@78cabae