Support metadata.short-description for Code skills

[cbusillo]

Objective

Code currently treats skill SKILL.md frontmatter as name plus description only. The newer Codex skill loader supports metadata.short-description, which is useful for compact UI surfaces while preserving description as the model-visible trigger/routing text.

Add Code-side support for metadata.short-description in the code-rs skill loader if it fits the current Code architecture.

Finish Line

Code can load an optional metadata.short-description from skill frontmatter, expose it through the relevant Code skill metadata type/API/UI surface, and continue using description as the full trigger description.

Current Status

State: Ready
Next action: Inspect code-rs/core/src/skills/loader.rs, code-rs/core/src/skills/model.rs, and any TUI/app-server skill listing surfaces; decide the smallest Code-native metadata shape.
Blocked by: None
Last verified: 2026-05-13 against local ../code checkout on branch stabilize/v0.6.98-known-good

Scope

• In: code-rs skill loading/model/API/UI support for optional metadata.short-description.
• In: Tests proving older skills with only name/description still load.
• In: Tests proving metadata.short-description is sanitized/validated consistently with Code skill metadata conventions.
• Out: Porting the full newer Codex agents/openai.yaml system unless the implementation review finds Code already needs it.
• Out: Changing model-visible skill trigger selection semantics.
• Out: Editing cbusillo/codex-skills directly from this issue.

Acceptance Criteria

• SKILL.md frontmatter may include:

metadata:
  short-description: concise human-facing summary

• Skills without metadata.short-description behave exactly as before.
• description remains the full model-visible trigger/routing text.
• Any compact skill picker/list UI can prefer short-description where appropriate.
• Tests cover missing metadata, valid short description, empty/invalid values, and existing two-field skills.
• If this support lands, open a follow-up issue in cbusillo/codex-skills requesting updates to the skill schema docs/validator and any skills that should add or rely on metadata.short-description.

Relationships

Related external repo: cbusillo/codex-skills.

Validation

Suggested validation:

• Run the relevant code-rs skill loader/unit tests.
• Run any TUI/app-server tests that serialize or display skill metadata.
• Manually verify one sample skill still appears with the expected full description and optional compact summary.

Decisions

• Code is the source of truth for this request; do not assume newer Codex behavior applies unless it is intentionally ported.
• Keep the first implementation narrowly focused on metadata.short-description.

Open Questions

• Which Code UI/API surfaces, if any, should display the compact summary immediately?