fix(harness): verify feature transition provenance across base and head

Parent: #384 (P1-2).

## Scope
Add lint-feature-transition --base --head for status/owner/evidence state transitions and their authorization provenance.

## Acceptance
- Illegal transitions and direct passing edits fail.
- Recomputed evidence fingerprints without trusted verification attestation fail.
- Legitimate harness verify output passes.
- PR CI evaluates the base-to-head transition, not only the final tree.

Delivery discipline: one issue, one worker branch, one PR.

Start with the lint-feature-transition entry point and the existing harness verify output, then inspect how PR CI evaluates changes between base and head. Trace the status, owner, evidence, and authorization provenance checks. Done means illegal or directly edited transitions and untrusted fingerprint recomputation fail, while legitimate verification passes.

Written by the indexing model from the issue text.