[Bug] Skill builder incorrectly validates frontmatter against outdated schema

Bug Description
the extend-skill-builder will often draw a definitive line in the sand and claim that some frontmatter attributes are invalid like disable-model-invocation or compatability/metadata. it should be better tuned to the official claude code docs https://code.claude.com/docs/en/skills#frontmatter-reference and agent skills spec https://agentskills.io/specification#frontmatter-required

Environment Info

• Platform: darwin
• Terminal: ghostty
• Version: 2.1.49
• Feedback ID: 9f166be2-3e0c-437b-a59e-80fd4d4dc5e2

Errors

[{"error":"Error: NON-FATAL: Lock acquisition failed for /Users/bill/.local/share/claude/versions/2.1.49 (expected in multi-process scenarios)\n    at PFR (/$bunfs/root/claude:2599:2098)\n    at iyA (/$bunfs/root/claude:2599:1209)\n    at processTicksAndRejections (native:7:39)","timestamp":"2026-02-20T16:37:13.191Z"}]