Skill length cap explorer

Drag the slider to see where a SKILL.md lands against tests/skills/test-skill-length.sh.

Lines: 500

0400 (preferred)500 (cap)

PASS — within 500-line cap.

PR #1576 trims src/skills/brainstorm/SKILL.md from 501 → 500 lines to unblock the Agents & Skills CI job for the open PR queue.