fix: enable JavaScript fallback on Windows

[hsjoberg]

Note

This pull request was authored by AI on behalf of @hsjoberg.

Summary

Hey. Reanimated previously routed React Native Windows through the JavaScript implementation introduced in #4917.

The fallback regressed after #8371 moved Worklets' native implementation to .native.ts files. Metro considers Windows a native platform and therefore selects .native before the unsuffixed JavaScript implementation. Before that change, IS_WINDOWS was included in SHOULD_BE_USE_WEB, causing Windows to select JSWorklets. Metro now selects NativeWorklets.native.ts, which expects a native Worklets module that React Native Windows does not provide.

#9893 later introduced the same platform split inside Reanimated.

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Restoring the PlatformChecker.ts approach as was previously used in #4917 and #4669 seems inadequate for the current codebase structure, because Metro resolves the .native module before that runtime check can execute.
This PR therefore extends wrapWithReanimatedMetroConfig so that internal relative imports from Reanimated and Worklets do not prefer .native files on Windows.

Windows-specific .windows files are still considered, followed by the unsuffixed JavaScript fallback. Resolution outside these two packages is unchanged, and existing custom Metro resolvers are preserved.

Test plan

• Added focused tests covering Reanimated and Worklets imports on Windows.
• Verified non-Windows, package, and external imports retain normal resolution.
• Verified delegation to both custom and default Metro resolvers.
• Bundled and ran blixt-wallet with React Native Windows 0.85.3 (new arch).
• Confirmed no Reanimated or Worklets .native modules are selected.
• Confirmed the JavaScript fallback works at runtime.

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No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: Repository UI

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Run ID: b993c44c-9172-4640-b2c2-9f33998698d3

📥 Commits

Reviewing files that changed from the base of the PR and between 993c65e and 5cdbf38.

📒 Files selected for processing (3)

• docs/docs-reanimated/docs/debugging/accurate-call-stacks.mdx
• packages/react-native-reanimated/__tests__/metroConfig.test.js
• packages/react-native-reanimated/metro-config/index.js

🚧 Files skipped from review as they are similar to previous changes (3)

• packages/react-native-reanimated/metro-config/index.js
• docs/docs-reanimated/docs/debugging/accurate-call-stacks.mdx
• packages/react-native-reanimated/tests/metroConfig.test.js

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📝 Walkthrough

Walkthrough

The Metro configuration now selects JavaScript Reanimated and Worklets implementations for matching React Native Windows imports. Tests cover resolver behavior, context preservation, pass-through cases, and default-resolver delegation. Documentation describes the fallback and its lack of native animations and a native Worklets runtime.

Merge Risk: ⚪ Minimal · up to 5cdbf

This PR adjusts Windows module resolution to use the JavaScript fallback for Reanimated and Worklets while preserving normal behavior elsewhere; no actionable merge-blocking risk remains beyond normal checks and review.

🚥 Pre-merge checks | ✅ 4

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes enabling the JavaScript fallback on Windows.
Description check	✅ Passed	The description accurately explains the Windows fallback, Metro resolution changes, tests, and runtime verification.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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