build: Make pnpm build-profile emit usable rspack stats

[ryan953]

pnpm build-profile did not produce a file anyone could analyze. The old script passed --profile, which rspack no longer accepts, and fixing the flag alone was not enough. rspack --json writes whatever the configured stats options describe, and the CLI gives you no flag to override them. rspack.config.ts set no stats, so the CLI filled in its own default — the errors-warnings preset, which it applies whenever stats is unspecified, independently of mode — and the JSON came out with no assets, chunks, or entrypoints in it at all. Setting stats without trimming it lands at the other extreme: module records carry their source text, which grew the output past 300MB.

RSPACK_STATS=1 now gates a trimmed stats object applied to both the app and service-worker configs. The env gate keeps normal builds and the dev server untouched, which seemed better than adding a second root-level config file just for profiling. The script also pins NODE_ENV=production and --mode production so the profile matches build-production, and it writes through --json=stats.rspack.json instead of a shell redirect so CLI logging cannot end up inside the JSON.

The gated block keeps the bundle shape: assets, chunks, chunk groups, entrypoints, and chunk parent/child/sibling relations, so the graph stays walkable. On the app compiler that is 5303 assets, 1684 chunks, the app, gsAdmin and sentry entrypoints, and 9 named chunk groups. Module records are included with source: false, so module identity and nesting survive while the source text that pushed the file past 300MB stays out.

The output file is gitignored.

https://claude.ai/code/session_01Jp2jDjcwahdDYBBSmWFVXc

[scttcper]

Review by Astra. The env gate and direct JSON file output look reasonable. Two suggestions below: retain module detail if this is intended for bundle analyzers, and clarify the CLI defaults in the comment and PR description.