feat: add non-linear navigation to Wizard

[ernst-dev]

Description

Adds an opt-in, backward-compatible allowNonLinearNavigation boolean prop to Wizard. When set to true, users can jump directly to any step ahead of the current one from the navigation pane, rather than only to previously-visited steps or optional steps skippable via allowSkipTo. This enables a non-linear navigation model where every step is directly reachable.

Implementation reuses the Wizard's existing step-status/event machinery — no new event reason or breaking change:

• A forward, not-yet-visited step now resolves to the existing Next status when allowNonLinearNavigation is on, so it renders as a focusable, non-aria-disabled navigation link.
• Navigating to such a step fires onNavigate with reason: 'skip' (already documented as navigating to a previously-unvisited step); visited steps continue to fire reason: 'step'.
• Forward navigation remains disabled while isLoadingNextStep is true.
• Fully backward compatible — defaults to false; allowSkipTo (the in-form skip-to button) is independent and can be combined.

Threaded through internal.tsx → wizard-navigation / wizard-step-navigation-expandable → wizard-step-list (getStepStatus), covering both visual-refresh and classic navigation panes plus the small-container expandable pane.

Related links, issue #, if available: Internal SIM AWSUI-61922.

⚠️ Ticket-mismatch note: SIM AWSUI-61922 currently resolves to an unrelated ticket (P416484847 — an "AWS-UI-Highcharts" bindle permission question). No Wizard navigation spec was available on the ticket, so this change was implemented per the provided feature description. Please confirm the intended scope.

How has this been tested?

• Added a dedicated Non-linear navigation unit-test suite in src/wizard/__tests__/wizard.test.tsx covering: all forward steps enabled when the prop is set, backward-compatibility (forward required steps stay disabled by default), reason: 'skip' on forward jumps to unvisited steps, reason: 'step' on navigating back to visited steps, and forward steps remaining disabled during isLoadingNextStep.
• Full Wizard unit suite green: 93/93 tests pass (jest -c jest.unit.config.js src/wizard/__tests__/).
• eslint clean on src/wizard and pages/wizard; quick-build (TypeScript) clean.
• Added dev page pages/wizard/non-linear-navigation.page.tsx for manual/visual verification, including keyboard navigation.

Review checklist

The following items are to be evaluated by the author(s) and the reviewer(s).

Correctness

• Changes include appropriate documentation updates. — Prop documented via JSDoc in interfaces.ts.
• Changes are backward-compatible if not indicated, see CONTRIBUTING.md. — Yes, opt-in, defaults to false.
• Changes do not include unsupported browser features, see CONTRIBUTING.md. — Yes.
• Changes were manually tested for accessibility, see accessibility guidelines. — Reuses existing focusable/aria-current/aria-disabled navigation-link semantics.

Security

• If the code handles URLs: all URLs are validated through the checkSafeUrl function. — N/A, no URL handling.

Testing

• Changes are covered with new/existing unit tests? — Yes (5 new unit tests).
• Changes are covered with new/existing integration tests? — Existing integration coverage unaffected; behavior validated via unit tests + dev page.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 97.61%. Comparing base (f97729a) to head (dfddcb5).
⚠️ Report is 2 commits behind head on main.

Additional details and impacted files

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  Coverage   97.61%   97.61%           
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  Files         952      952           
  Lines       30816    30819    +3     
  Branches    11318    11321    +3     
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+ Hits        30081    30084    +3     
  Misses        688      688           
  Partials       47       47           

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