Document cache strategies

Always provide clear documentation and implementation for caching strategies, including key generation, invalidation policies, and default behaviors. When implementing caching:

1. Choose appropriate cache keys that balance specificity and reusability:
   • For CI environments, consider using commit SHA with restore-keys fallback: ```yaml
   • uses: actions/cache@v4 with: path: .turbo key: $-turbo-$ restore-keys: | $-turbo- ```
2. Document cache configuration options explicitly:
   • Explain what happens when cache configuration is missing
   • Specify available cache sources and their permissions (e.g., local vs. remote)
   • Describe the behavior of cache invalidation
3. Make cache behavior predictable and configurable:
   • Allow users to control cache sources (e.g., --cache=local:rw,remote:r)
   • Provide clear indicators when caching is enabled/disabled
   • Document which artifacts will be cached by default

Proper cache strategy documentation prevents unexpected behavior, improves performance, and gives users control over how and where their data is cached.