[danew]

Summary

Fix the false installed_paths: 0 result for standard OpenCode workspace skills.

• Detect .opencode/skills/<name>/SKILL.md in the active project and ancestor directories up to the nearest Git worktree root.
• Recognize project .agents/skills and .claude/skills compatibility sources.
• Use $XDG_CONFIG_HOME/opencode/skills (falling back to ~/.config/opencode/skills) for global OpenCode skills.
• Recognize directory-based and flat Markdown skill files, including symlinked installs.
• Stop treating opencode/agents/<name>.md agent definitions as installed skills.

The existing skills paths, skills list, skills doctor, and skill-open lookup share this detection. No installer, auth, dependency, or eval tooling changes are included. Arbitrary configured skill directories/catalogs are not parsed by this conventional-path diagnostic.

This is separate from device-auth PR #120.

Verification

• Real-binary, offline integration tests cover paths/list/doctor, XDG overrides, project ancestors, Git-worktree boundaries, agent-definition exclusion, and symlinked skills.
• cargo test --lib --test skills_discovery --test cli_blackbox: 371 library tests, 48 black-box tests and four new discovery tests passed; eight pre-existing ignored tests remain ignored.
• cargo clippy --all-targets -- -D warnings -A clippy::cognitive_complexity passed.
• Formatting and diff checks passed.