feat: add readOnly prop to PayrollOverview

[dmortal]

Summary

Adds a readOnly prop to PayrollOverview so a partner can render a submit-only review
of a specific, already-calculated payroll — hiding Edit and Cancel while keeping Submit
and receipt/paystub actions available. This brings the SDK to parity with gws-flows'
RUN_PAYROLL_READ_ONLY flow type, which similarly locks a payroll deep link down to
show/submit only (no edit, no cancel).

Changes

• PayrollOverview: new readOnly?: boolean prop (default false); when set, suppresses
  the Edit action, the processing-failure retry CTA, and folds into the existing
  cancellability check so Cancel is hidden too.
• PayrollOverviewPresentation: new canEdit?: boolean prop (default true) gating the
  Edit button, mirroring the existing canCancel pattern.
• Added test coverage for both components and a new PayrollOverviewReadOnly Storybook story.
• Regenerated docs/reference/payroll/blocks.md from updated TSDoc.

Testing

• npm run test -- --run src/components/Payroll/PayrollOverview — 40 tests pass, including
  new cases for Edit/Cancel suppression and Submit remaining functional in read-only mode.
• npx tsc --noEmit and npx eslint — clean (only a pre-existing, unrelated
  exhaustive-deps warning).
• npm run docs:build — docs site builds cleanly with the regenerated reference.
• Storybook: PayrollOverviewReadOnly story under Domain/Payroll/PayrollOverview shows the
  submit-only actions row.

🤖 Generated with Claude Code