chore: add cursor agent rules

[thomasrockhu-codecov]

Summary

Adds four always-on Cursor AI agent rules to .cursor/rules/:

• pre-commit-checks — run ruff check --fix and ruff format before every commit/PR
• small-prs — break large changes into focused, stacked draft PRs
• learn-workflow — automatically capture workflow lessons as new rules
• learn-technical — automatically capture codebase-specific technical learnings as new rules

Test plan

• Verify rules appear in Cursor's rule picker
• Confirm alwaysApply: true activates them in every session

Made with Cursor

---

Note

Low Risk
Docs/config-only changes under .cursor/rules/ that affect developer/agent workflow but not runtime behavior.

Overview
Adds four always-on Cursor rules under .cursor/rules/ to standardize developer/agent workflow: run ruff lint/format before commits/PRs, keep changes split into small/stacked PRs, and capture both workflow and codebase-specific technical learnings as new/updated rules.

No application code changes; this PR only introduces agent guidance documentation/config.

^{Written by Cursor Bugbot for commit 937b138. This will update automatically on new commits. Configure here.}