Schema validation consolidated into @fjell/core/validation

This release centralizes schema validation in @fjell/core/validation and updates library internals and docs accordingly. It also includes minor dependency updates.

Improvements

• Consolidate schema validation to @fjell/core/validation (d89b432)
  • Delete local validation module: removed src/validation/schema.ts
  • Update ops to use core validation utilities: validateSchema now imported from @fjell/core/validation in src/ops/create.ts and src/ops/update.ts
  • Import SchemaValidator from @fjell/core/validation in src/Options.ts, remove local interface, and re-export the type for convenience

Documentation Updates

• Update docs/VALIDATION.md to reference @fjell/core/validation and link to core validation docs (d89b432)
  • Note that schema validation (validateSchema and SchemaValidator) is part of @fjell/core and can be used independently (e.g., in cache layers or APIs)
  • Example updated to import and type SchemaValidator appropriately

Dependency Updates

• Bump @fjell/core from ^4.4.64 to ^4.4.65 and @fjell/registry from ^4.4.70 to ^4.4.71 (790e996)