refactor(skills): migrate skills to agent-skills-nix

[ryoppippi]

Summary

Migrate skills management from local .claude/skills/ directory to Nix-based management using agent-skills-nix.

What Changed

• Remove local skills directory from git tracking
• Add agent-skills-nix and StackOneHQ/skills as flake inputs
• Configure devShell to auto-install skills via symlink-tree
• Update .gitignore to exclude Nix-managed skill directories
• Update CLAUDE.md to document the new skills management approach

Why

• Centralise skills in StackOneHQ/skills repository for reuse across projects
• Leverage Nix for reproducible, declarative skill installation
• Skills are automatically installed as symlinks when entering nix develop

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Summary by cubic

Migrated skills management from the local .claude/skills directory to agent-skills-nix, sourcing from StackOneHQ/skills and auto-installing symlinked skills to .claude/skills and .agents/skills on nix develop for Codex compatibility. This removes tracked skill files and makes setup reproducible.

• Refactors

  • Stop tracking .claude/skills and .agents/skills; add both to .gitignore.
  • Configure flake to discover and allowlist just-commands and release-please; install via symlink-tree to both targets in devShell.
  • Update CLAUDE.md to document Nix-managed skills.

• Dependencies

  • Add agent-skills-nix and StackOneHQ/skills as flake inputs.
  • Update flake.lock for new and bumped inputs.

^{Written for commit 85e3342. Summary will update on new commits.}

[Copilot]

Pull request overview

This PR migrates Claude skills management from in-repo .claude/skills files to a Nix-based setup using agent-skills-nix and the shared StackOneHQ/skills repository. It updates the Nix flake to automatically install skills as symlinks on nix develop, documents the new approach, and removes now-redundant local skill definitions.

Changes:

• Add agent-skills-nix and StackOneHQ/skills as flake inputs, wire up catalog/selection, and integrate agentLib.mkShellHook plus mkBundle into the devShell so .claude/skills is populated as a symlink-tree.
• Adjust treefmt’s oxfmt configuration to pass --no-error-on-unmatched-pattern and simplify shell messages while keeping existing pre-commit and tooling behavior intact.
• Document Nix-managed skills in CLAUDE.md, ignore .claude/skills in .gitignore, and remove the local release-please and just-commands SKILL definitions in favor of the centralized skills repo.

Reviewed changes

Copilot reviewed 4 out of 6 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
flake.nix	Adds agent-skills and stackone-skills inputs, builds a skills catalog/allowlist/selection, configures a bundle and local targets, and extends the devShell shellHook to install skills into .claude/skills as a symlink tree.
flake.lock	Pins agent-skills-nix, StackOneHQ/skills, and their transitive inputs (e.g. home-manager) and refreshes existing flake input revisions to align with the new configuration.
CLAUDE.md	Updates the description of .claude/skills to note Nix-based management via agent-skills-nix and StackOneHQ’s skills repo while keeping the skills tables consistent with the new source of truth.
.gitignore	Ignores .claude/skills so the Nix-managed symlink tree is not tracked in Git.
.claude/skills/release-please/SKILL.md	Removes the in-repo release-please skill definition, deferring to the shared skills repository.
.claude/skills/just-commands/SKILL.md	Removes the in-repo just-commands skill definition, also deferring to the shared skills repository.

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[cubic-dev-ai]

No issues found across 6 files