ci: automatically label each PR with a code-size bucket

[michaelmalave]

Summary

This adds a small GitHub Actions workflow that automatically tags every pull request with a size label (size/XS through size/XL) so reviewers can see how big a PR is before they open it. The size is based only on lines of code changed — documentation, the lockfile, and generated files don't count — so a big docs update or a lockfile bump won't make a small code change look large. The label is purely informational: it never blocks a PR from merging.

What it does, step by step:

• Runs automatically whenever a PR is opened, updated, or reopened.
• Counts the lines added and removed in the PR and picks a size bucket: XS (under 10), S (under 100), M (under 500), L (under 1000), XL (1000+). These thresholds are constants at the top of the file, so they're easy to change.
• Ignores docs/, *.md, package-lock.json, autocomplete-scripts/, and dist/ when counting, so the size reflects code a person actually has to review.
• Adds a separate docs label when documentation changed, tracked independently of size.
• Keeps exactly one size label on the PR at a time, updating it as the PR grows or shrinks.

Comments on the PR

The workflow posts a comment only when a PR is XL (1000+ lines of code churn) — no other size gets a comment. It's posted once, and it's automatically deleted if the PR is later updated and drops below XL. The comment is a suggestion, not a gate; the check still passes either way. The exact text is:

This PR is labeled size/XL (N lines of code churn, excluding docs, package-lock.json, and generated files).

Large PRs are harder to review well. If it can be split into smaller, independently reviewable pieces, consider doing so. This is a suggestion, not a blocker — the check still passes.

The workflow is plain bash using the built-in gh CLI (the same zero-dependency style as pr-title-check.yml); it pulls in no third-party actions.

Type of Change

Breaking Changes (major semver update)

• Add a ! after your change type to denote a change that breaks current behavior

Feature Additions (minor semver update)

• feat: Introduces a new feature to the codebase

Patch Updates (patch semver update)

• fix: Bug fix
• deps: Dependency upgrade
• revert: Revert a previous commit
• chore: Change that does not affect production code
• refactor: Refactoring existing code without changing behavior
• test: Add/update/remove tests

The real type is ci (a CI-only change, accepted by the PR-title linter). The template has no ci box, so the closest one (chore) is checked. No production code is touched.

Testing

Steps:

1. On this PR, expect a size/* label to be applied automatically. Since this change touches no docs/ or *.md files, no docs label should appear. (This PR is size/M, so no comment is posted.)
2. To see the docs behavior, push a follow-up commit editing a docs/*.md file — expect the docs label to show up while the size label stays driven by code changes only.

Screenshots (if applicable)

Related Issues

GitHub issue: none
GUS work item: none

[eablack]

Automated review findings for the new pr-size-label.yml workflow, posted inline below (most severe first). The line 39 runner-pool exposure is the one worth gating the merge on.