ci: add PR size check and label workflow

[notgitika]

Description

Adds a GitHub Actions workflow that automatically labels PRs with size categories (size/xs through size/xl) based on changed lines. Excludes lockfiles and snapshots from the count. Auto-creates missing labels with color coding. Warns on extra-large PRs without blocking merge.

Related Issue

N/A

Documentation PR

N/A

Type of Change

• New feature

Testing

• Manually verified workflow YAML syntax
• I ran npm run test:unit and npm run test:integ
• I ran npm run typecheck
• I ran npm run lint

Checklist

• I have read the CONTRIBUTING document
• My changes generate no new warnings
• Any dependent changes have been merged and published

---

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the
terms of your choice.

[github-actions]

Coverage Report

Status	Category	Percentage	Covered / Total
🔵	Lines	41.28%	2657 / 6435
🔵	Statements	40.74%	2786 / 6838
🔵	Functions	43.52%	571 / 1312
🔵	Branches	46.81%	1765 / 3770

Generated in workflow #1 for commit 53c2a5c by the Vitest Coverage Report Action