Summary

In browser watch mode, configuring setupFiles alongside test files that import heavy libraries (e.g. @testing-library/react) triggers an HMR fallback reload with a noisy console warning. The root cause is that lazyCompilation was applied uniformly to all modules — when a setup file's lazy proxy activates, the resulting chunk graph update propagates through an entry.ts boundary that has no module.hot.accept() handler, causing Rspack HMR to abort and fall back. This PR excludes resolved setup file paths from lazyCompilation.test so they are compiled eagerly, while test files remain lazy (preserving O(1) initial compile time).

Behavior diff:

watch mode + setupFiles:   HMR fallback warning on startup  →  clean start, no warning
test files (no setupFiles): lazy compilation unchanged       →  unchanged

Changes:

• createBrowserLazyCompilationConfig(setupFiles) — new helper that builds the lazyCompilation config with a test predicate excluding setup file paths
  • no-op (no test field) when setupFiles is empty, preserving existing behavior
• createBrowserRuntime — resolves setup files before building the merged Rsbuild config and passes them into the new helper
• e2e regression: browser-react fixture extended with setupFiles + a test importing @testing-library/react; watch.test.ts asserts no HMR warning on startup
• unit tests for createBrowserLazyCompilationConfig covering empty, single, and cross-platform path cases