Fix the livekit_uniffi build hook for universal builds and allow code_assets 2.x

[hiroshihorie]

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PR description

Three fixes to the livekit_uniffi Dart package templates, found while doing the manual first publish of 0.1.10 and wiring it into client-sdk-flutter. All ship with the next release.

• Allow code_assets 2.x. The pubspec capped code_assets below 2.0.0, which shipped on Aug 18. Its only breaking change (equality on OS/Architecture) does not affect the hook, and a cap below the current major makes the package unresolvable next to any dependency that already requires 2.x. Now >=1.0.0 <3.0.0. The comment is updated: hooks 2.2.0 dropped its meta dependency, so the Flutter meta-pin back-solve that motivated the wide ranges mostly no longer applies, but wide bounded ranges remain the right shape.
• Stop registering the downloaded library as a hook dependency. Dependencies are inputs. Registering the downloaded output made the hooks runner print "File modified during build. Build must be rerun." and run the hook, and the download, twice on every fresh consumer build. Local mode keeps its registration, where the library really is an input.
• Keep each target's downloaded library in its own directory. The hook wrote every target's library to the same path under the shared output directory. A universal macOS release build runs the hook once per architecture and then merges the results with lipo, so the second download overwrote the first and the build failed with "have the same architectures (x86_64) and can't be in the same fat output file" (Integrate initial uniffi rust core client-sdk-flutter#1160's macOS CI job). The directory is now keyed by target triple, which is also how the hooks package documents the shared directory should be used.

Breaking changes

None.

MSRV

No changes.

Testing

From this branch, cargo make dart-package in both profiles:

• Dev profile (local library): resolves code_assets 2.0.0 + hooks 2.2.0, 5/5 FFI tests pass.
• Release profile, copied outside the repo like the publish workflow does: fresh dart test downloads the real 0.1.10 library from the release, the "File modified during build" rerun is gone, 5/5 tests pass, and dart pub publish --dry-run reports 0 warnings.
• Universal build: the client-sdk-flutter example pointed at the regenerated package with a path override, flutter build macos --release. Builds, lipo -info on the bundled livekit_uniffi.framework reports x86_64 arm64, and the hook produced separate aarch64-apple-darwin and x86_64-apple-darwin output directories. Debug builds are single-architecture and cannot catch this, which is why it reached CI.
• code_assets 2.0.0 also adds header validation of the bundled library against the target architecture, which the downloaded 0.1.10 dylib passed.

Async

No async code changed.

🤖 Generated with Claude Code

[github-actions]

Changeset ✓

This PR includes a changeset covering all affected packages:

Package	Bump
livekit-uniffi	patch

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