ci: report binary size change on pull requests

[elecmonkey]

Summary

Nothing in CI tells a reviewer how much a pull request grows the binary. This reports it, with no added build and no repository configuration.

How it works

• Measure — Test npm packages already compiles everything behind ./cmd/rslint, so a release relink right after Build is link-only off the warm cache: 49s against 5m12s for a full build. It relinks rather than measuring the binary that job already produced, which is 52.20 MiB unstripped where the released one is 37.10 MiB.
• Store — every run, main included, uploads its measurement as a workflow artifact. No repository writes, no token beyond the built-in GITHUB_TOKEN.
• Compare — a pull request's baseline is the artifact of the main run for its base commit. The new Binary Size job reads both, writes the comparison to the job summary, and updates one pull request comment in place.

The job is deliberately absent from CI Done — porting a rule legitimately grows the binary, so this informs a review rather than blocking a merge.

Limits

• A fork's token is read-only, so the comment step fails there by design and the job summary is the report.
• Artifacts expire, so this covers the per-pull-request comparison; the long-term main trend still needs somewhere durable to write.

Related Links

Closes #2059

Checklist

• Tests updated (or not required).
• Documentation updated (or not required).

Token scope in the Binary Size job

The trigger is pull_request, never pull_request_target: a fork's token is capped read-only regardless of the permissions: block, and a same-repo author already has push access. The pull-requests: write token crosses no privilege boundary.

[github-actions]

🦀📦 Binary size

Commit b90a29d merged into base 0e15fa6 — feat(jest,rstest): add prefer-lowercase-title rule (#2197).

Binary	Base	This PR	Change
rslint (linux-x64-gnu)	—	39.23 MiB	—

_{Stripped go build -ldflags="-s -w" ./cmd/rslint, Go 1.26.0, linux/amd64 · run · 2026-09-20 09:09 UTC}

[elecmonkey]

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[chatgpt-codex-connector]

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