feat: add hierarchical skill group selector

[creatiVision]

Context

Add a hierarchical skill group selector for the command in Kimi Code CLI.

Summary of Changes

1. Metadata Extension: Extended SkillMetadata and SkillSummary with optional fields: category, issuer, collection, groups, and tags. Updated summarizeSkill to project these metadata fields.
2. Pure Skill Group Tree Model: Created skill-group-tree.ts implementing group resolution precedence (groups -> category -> relative folder path -> Uncategorized fallback) and hierarchical group node building.
3. TUI Skill Selector Component: Created SkillSelectorComponent based on ModelSelectorComponent and ChoicePicker UI patterns, offering breadcrumb header navigation, search filtering, up/down item selection, escape navigation (back level / exit), and description preview footers.
4. Command Integration: Registered /skill in built-in slash command dispatch while preserving direct skill invocation (e.g. /skill:cv_ssh-ops).
5. Tests & Changeset: Added unit test suites for metadata propagation, tree resolution, and selector component navigation, plus a changeset file.

Verification

• pnpm test: 57 test files passed (648 tests).
• pnpm typecheck: Passed without errors.
• pnpm lint: Passed with 0 errors.