fix: add explicit document review acceptance

[julismo]

What changed

• Added an explicit, accessible Accept review action to the synthetic document-review flow.
• Shows a local-only confirmation and clears it when a correction changes the reviewed result.
• Added behaviour tests and a real synthetic-workbench screenshot to the README.

Why

The approved showcase design requires a reviewer to accept or correct a result. The panel previously exposed correction only.

User impact

Acceptance stays in React component state: no data is uploaded, stored, or sent to an external service.

Validation

• npm run lint
• npm run typecheck
• npm run test (14 passing)
• npm run build
• Browser checks at 1440px and 375px with zero console errors or warnings