Fix FocusZone Shift+Tab traversal from first-child containers

[Jason Morse (JasonVMo)]

Fixes #4317

Platforms Impacted

• iOS
• macOS
• win32 (Office)
• windows
• android

The production fix is Windows Fabric-only. Native regression coverage is shared across Windows, Win32, and macOS because outside-zone Tab navigation is a shared contract. macOS uses an independent AppKit key-view loop that excludes the zone; Win32 uses its host-provided FocusZone. Neither native implementation is changed.

Description of changes

• Keep reverse-preorder traversal, but accept a focus candidate only when it is the visited node itself. Searching an ancestor's entire subtree could previously re-enter the zone or select a later sibling.
• Add a native first-child regression scene with nested non-collapsible containers, later siblings at both levels, and a preceding focusable subtree. Assert Shift+Tab exits from both the first and last zone items to the preceding outside control.
• Cover preceding-sibling backward exit and forward Tab exit while retaining the existing linear and geometric navigation cases.
• Update the FocusZone specification and add a patch changeset.

Verification

Before	After
The new Windows Fabric regression fails: Shift+Tab does not focus the preceding outside button.	The same native regression passes with the fix.

• Windows Fabric: native build/bundle and smoke lifecycle pass; 156 stories render; all 5 FocusZone native cases pass, 0 fail, 0 skip.
• Win32 Paper: smoke lifecycle passes; 150 stories render; all 5 FocusZone native cases pass, 0 fail, 0 skip.
• macOS: production story bundle and test discovery pass. Native macOS execution was not available on the Windows development host.
• FocusZone package: format, lint, build, and 9 tests pass.
• Agentic components: format, lint, build, story type checks, 440 tests, and 8 snapshots pass.
• Storybook format/lint, changeset validation, and diff checks pass.

Native smoke runs used a temporary wdio.story: 'native-focuszone--*' selector, removed before this commit. Owned app, Metro, and driver processes were cleaned up.

Pull request checklist

This PR has considered (when applicable):

• Automated Tests
• Documentation and examples
• Keyboard Accessibility
• Voiceover
• Internationalization and Right-to-left Layouts

Windows CI follow-up

Commit 279722f8f fixes the separate legacy Windows E2E startup failure. The failed job installed windows@6.3.0 outside the Yarn lockfile, then could not import the driver's appium/driver.js peer dependency; no UI tests ran.

Both Windows endpoints now use APPIUM_HOME=. and the existing Yarn-managed Windows driver. Preparation validates its registered version, resolved package path, and actual dynamic import, and WDIO loads only the Windows driver. Other platforms retain their existing setup.

The three setup regression checks pass through both preparation commands. The old isolated Appium home is rejected as expected. A real Appium server successfully loaded the locked driver and answered /status, then was stopped. E2E lint/build, the root build, formatting, and changeset validation pass. Broader local repository lint reports Knip unused-dependency errors in untouched workspaces; this follow-up does not alter those packages. Full native Windows E2E confirmation is delegated to the new CI run because WinAppDriver is not installed locally.

[github-actions]

Bundle size report

Tree-shaken production Metro bundles. Component costs are relative to their platform shell; shell costs are absolute.

Platform	Scenario	Baseline cost	Current cost	Cost delta	Change	Gzip delta	Module delta
macos	shell	801.3 KiB	801.3 KiB	0.0 KiB	0.00%	0.0 KiB	+0
macos	components-button	50.1 KiB	57.4 KiB	+7.3 KiB	+14.58%	+2.3 KiB	+17
macos	components-catalog	267.3 KiB	281.6 KiB	+14.3 KiB	+5.35%	+5.1 KiB	+24
macos	design-theme-state	33.3 KiB	33.7 KiB	+0.4 KiB	+1.34%	+0.2 KiB	+6
macos	design-themed-root	New	36.1 KiB	New	New	New	New
macos	design-color-lib	7.1 KiB	7.1 KiB	0.0 KiB	0.00%	0.0 KiB	+0
macos	design-theme-state-legacy-source	35.3 KiB	35.8 KiB	+0.4 KiB	+1.26%	+0.1 KiB	+6
macos	design-legacy-theme-from-flex	100.2 KiB	100.7 KiB	+0.4 KiB	+0.45%	+0.1 KiB	+6
windows	shell	810.2 KiB	810.2 KiB	0.0 KiB	0.00%	0.0 KiB	+0
windows	components-button	50.0 KiB	57.2 KiB	+7.2 KiB	+14.43%	+2.4 KiB	+17
windows	components-catalog	267.0 KiB	281.2 KiB	+14.2 KiB	+5.31%	+5.1 KiB	+24
windows	design-theme-state	33.2 KiB	33.7 KiB	+0.5 KiB	+1.36%	+0.1 KiB	+6
windows	design-themed-root	New	36.0 KiB	New	New	New	New
windows	design-color-lib	7.1 KiB	7.1 KiB	0.0 KiB	0.00%	0.0 KiB	+0
windows	design-theme-state-legacy-source	35.3 KiB	35.7 KiB	+0.4 KiB	+1.27%	+0.1 KiB	+6
windows	design-legacy-theme-from-flex	100.0 KiB	100.4 KiB	+0.4 KiB	+0.44%	+0.1 KiB	+6

The job is advisory: size changes are reported but do not fail the pull request. Bundle or analysis errors still fail.

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