Use dedicated Android npm package

[j178]

Revert the shared Linux/Android musl package handling from 7f44e09.

Add a dedicated @j178/prek-android-arm64 platform spec that reuses the aarch64-unknown-linux-musl artifact without package-level libc metadata, so npm can install it on Android/Termux.

Follow-up to #1977

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 92.22%. Comparing base (7f44e09) to head (2d01943).
⚠️ Report is 1 commits behind head on master.

Additional details and impacted files

@@           Coverage Diff           @@
##           master    #1982   +/-   ##
=======================================
  Coverage   92.21%   92.22%           
=======================================
  Files         116      116           
  Lines       23338    23338           
=======================================
+ Hits        21522    21524    +2     
+ Misses       1816     1814    -2     

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[Copilot]

Pull request overview

This PR updates the npm distribution metadata so Android/Termux (process.platform=android) installs and runs prek by selecting a dedicated Android optionalDependency package, while still reusing the existing aarch64-unknown-linux-musl artifact.

Changes:

• Split the previous combined Linux/Android arm64 musl handling into a Linux-only musl package plus a new @j178/prek-android-arm64 package.
• Adjust npm platform package package.json generation to always emit libc when specified (and omit it for the Android package).
• Simplify libc matching in npm/bin/prek.js to a direct spec.libc comparison.

Reviewed changes

Copilot reviewed 1 out of 2 changed files in this pull request and generated 1 comment.

File	Description
scripts/build-npm-packages.py	Adds a dedicated Android arm64 PlatformSpec and adjusts package.json libc emission behavior.
npm/bin/prek.js	Removes the Android-specific libc matcher and relies on platform-specific packages for selection.