v2.0.0 - Harness-agnostic Agent Skills

Muster is now distributed as plain Agent Skills, so it runs in Claude Code, Cursor, Codex, Gemini CLI, Mistral, pi, and any other harness that reads the spec - not just Claude Code.

Highlights

• commands/*.md → skills/<name>/SKILL.md as a single source of truth. The seven command bodies are unchanged; the only frontmatter addition is disable-model-invocation: true, keeping each command slash-only (the model never auto-fires /build or /triage). Other harnesses ignore the unknown field.
• install.sh now symlinks skills into ~/.claude/skills/.
• README + CONTRIBUTING rewritten harness-agnostic, with a "Runs in" badge row and an "Other harnesses" install section.

Upgrading (breaking)

• Plugin users: /plugin marketplace update muster then /plugin update muster@muster. Invocation is unchanged (/muster:think, …).
• Symlink users: the install target moved from ~/.claude/commands/ to ~/.claude/skills/. Re-run install.sh (it pulls, then relinks); you can remove the old dangling ~/.claude/commands/<muster>.md symlinks.

Notes

• The previous command-based line is preserved on the legacy/commands branch.