Shareable instruction files for Cursor, Claude Code, Copilot, Windsurf, and more — installed alongside your existing agent rules.
ALWAYS create new objects, NEVER mutate existing ones: WRONG: modify(original, field, value) → changes original in-place CORRECT: update(original, field, value) → returns new copy with change Rationale: Immutable data prevents hidden side effects, makes debugging easier, and enables safe concurrency.