Add skill catalog installer for cross-provider consumption

[MSicc]

Summary

Add an installer/distribution layer so this repository can be consumed as a skill catalog, not only maintained as a canonical source of skills.

Problem

The repository already defines skills/ as the canonical source of workflow logic, but consumers currently need to clone the repo and manually copy skill folders into their target environment. That is too much friction for catalog-style reuse across providers and tools.

Proposal

Introduce a thin installer that distributes canonical skills from this repo into provider-specific or generic target locations without making the installer a second source of truth.

Goals

• Keep skills/ as the only canonical source of skill definitions
• Support catalog-style consumption of skills from this repo
• Allow selective install of one skill or multiple skills
• Support provider adapters or generic filesystem export targets
• Validate skills before installation
• Provide a dry-run mode
• Document consumer installation workflow in the README

Non-Goals

• Moving canonical skill logic into installer scripts
• Embedding provider-specific behavior inside each skill
• Replacing the existing skills-first authority model

Suggested Scope

• Add a catalog manifest (for example skills/catalog.json or skills/catalog.toml)
• Add an installer CLI/script under scripts/
• Support commands such as:
  • list
  • install <skill>
  • install --all
  • update
  • --target <provider|path>
  • --dry-run
• Add README documentation for consumers

Acceptance Criteria

• A user can discover available installable skills from the repo
• A user can install one named skill into a target location
• A user can install all supported skills into a target location
• Installation preserves canonical skill folder contents
• Validation is run or enforced before install
• The installer is documented and does not become a parallel source of workflow truth

Notes

This should reinforce the current architecture:

• skills/ remains canonical
• prompts/ remain thin wrappers
• installer logic handles packaging and placement only