Add caching strategy skill

[PAMulligan]

Description

Create a new skill that generates caching middleware and strategies for Nerva APIs. This complements the existing `api-performance` skill with dedicated caching patterns.

Why

The `api-performance` skill mentions caching but doesn't provide a dedicated, comprehensive caching implementation. A caching skill would generate middleware for in-memory caching, Redis, and Cloudflare KV with proper cache invalidation patterns.

Acceptance Criteria

• Create `.claude/skills/caching-strategy/SKILL.md`
• Cover caching strategies:
  • In-memory caching (Map-based, for single-instance Node.js)
  • Redis caching (for multi-instance Node.js)
  • Cloudflare KV caching (for Workers)
  • HTTP cache headers (Cache-Control, Vary)
• Generate Hono middleware that:
  • Caches GET responses by URL + query params
  • Supports TTL configuration per route
  • Handles cache invalidation on mutations (POST/PUT/DELETE)
  • Adds `X-Cache: HIT/MISS` response header
• Include cache key generation patterns
• Add stale-while-revalidate pattern
• Update `pipeline.config.json` with caching configuration section
• CI passes

[github-actions]

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[github-actions]

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