feat: Add priority and category metadata to all skill frontmatter

[mcj-coder]

Summary

Add standardized metadata.priority and metadata.type fields to all 55 skill frontmatter per SKILL-FORMAT.md.

Priority Model (from SKILL-FORMAT.md)

Priority	Category	Description
P0	Safety & Integrity	Security, immutability, provenance, traceability
P1	Quality & Correctness	Behavioral correctness, clean builds, test validity
P2	Consistency & Governance	Conventions, versioning, pipeline conformance
P3	Delivery & Flow	Incremental execution, developer experience
P4	Optimization & Convenience	Ergonomics, non-critical improvements

Type Categories

Type	Description
Process	Workflow and methodology guidance
Implementation	Technology-specific patterns
Platform	Platform/tooling integration
Quality	Code quality and standards

Acceptance Criteria

• All 55 skills have metadata.type field (PR #395)
• All 55 skills have metadata.priority field (PR #395)
• npm run lint passes (evidence)
• Values are appropriate for each skill's purpose (evidence)

[mcj-coder]

Plan

Simple bulk update - add metadata fields to all skill frontmatter:

1. Categorize skills by type (Process, Platform, Quality, Implementation)
2. Assign priority based on skill purpose (P0-P4)
3. Add metadata block to each skill's frontmatter
4. Verify lint passes

Plan approved. Proceeding with implementation.