fix(linter): prevent memory leak in resolver cache during language server usage

[Copilot]

Problem

The oxc language server was experiencing severe memory leaks when using the import plugin, with memory usage growing by 1-40MB per file open/close cycle and reaching several gigabytes over time. This was reported in issue #10627 where users observed the oxc_language_server process consuming 6.7GB of memory after an hour of usage.

Root Cause

Through ASAN analysis by @Brooooooklyn, the leak was traced to oxc_resolver::fs_cache::FsCache which caches filesystem metadata globally for performance optimization. In the language server context, where files are processed repeatedly via Runtime::run_source(), this cache would accumulate indefinitely without cleanup:

• Location: crates/oxc_linter/src/service/runtime.rs:976 where resolver.resolve(dir, specifier) is called
• Trigger: Only occurs when import plugin is enabled and resolver performs module resolution
• Pattern: Each React/JSX file with imports (especially @react-three/fiber) would add to the cache

Solution

Added strategic cache clearing at the end of Runtime::run_source() method:

// Clear resolver cache to prevent memory leaks in language server usage.
// The resolver caches filesystem metadata globally, which can accumulate
// indefinitely when processing files repeatedly in a language server context.
// Clearing after each run prevents unbounded memory growth while still
// allowing caching within a single linting session.
if let Some(resolver) = &self.resolver {
    resolver.clear_cache();
}

This approach:

• ✅ Prevents unbounded memory growth in language server usage
• ✅ Preserves performance benefits of caching within single linting sessions
• ✅ Only affects language server context, not CLI usage
• ✅ Uses the existing clear_cache() API provided by oxc_resolver

Testing

• Added integration test to verify cache clearing functionality
• All 746 existing linter tests continue to pass
• Test fixture from original issue reproduction is included

Impact

This fix resolves the memory leak that was making the oxc language server unusable for extended development sessions, particularly when working with React/JSX projects that heavily use imports.

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[codspeed-hq]

CodSpeed Instrumentation Performance Report

Merging #12674 will not alter performance

_{Comparing copilot/fix-cd26e7a8-3eeb-40b6-8d2a-0e25fec424e8 (e97c005) with main (7c1ff78)}

Summary

✅ 34 untouched benchmarks