feat(catalog): dynamic skill catalog installation via 'contextos skill add'

[kok-o]

Problem Statement

In \�2.0.0, the default installation profile was streamlined into a clean 'Neutral Bootstrap' (containing only the 7 core governance and workflow skills) to eliminate opinionated bloat.

The documentation and \AGENTS.md\ reference catalog skills (such as
eact, \ ypescript, \astapi, \docker, \system-design, etc.) that developers can install on demand. Currently, installing extra skills requires manual copying or using older plugin mechanics.

Objective

Implement the official \contextos skill\ CLI command suite to search, add, list, and remove domain skills directly from the versioned catalog (
egistry.v2.json).

Scope of Work

1. CLI Commands:
   • \contextos skill add : Validates against
     egistry.v2.json, installs skill into .agents/skills//, and regenerates adapters.
   • \contextos skill remove : Safely removes managed skill files while preserving custom modifications as .contextos.backup.
   • \contextos skill list: Displays installed vs available catalog skills with descriptions and token impact.
2. Dependency Resolution:
   • Validate skill dependencies specified in \skill.yaml\ (e.g. installing
     eact\ prompts or resolves \ ypescript).
3. Lockfile & Attestation:
   • Update .agents/lockfile.v2.json\ with the installed skill's content hash and origin.

Acceptance Criteria

• \contextos skill add \ successfully downloads and installs valid skills from the catalog.
• Running \contextos skill add react\ compiles rules for all active adapters (.cursorrules, copilot-instructions, etc.).
• Tests verify safe install, conflict detection, and clean uninstallation.