fix: preserve unknown fields in Anthropic schemas (restores prompt caching) (#74)

fix: preserve unknown fields in Anthropic schemas (restores prompt caching) (#74)

* fix: preserve cache_control in Anthropic schemas to restore prompt caching

* fix: add biome-ignore for passthrough tests, extend fix to OpenAI

- Add biome-ignore comments to suppress noExplicitAny in tests
  (required for testing unknown field preservation)
- Add .passthrough() to OpenAI schemas for consistency
  (OpenAIMessageSchema, OpenAIContentPartSchema)
- Format Anthropic schemas to match project style

* test: add OpenAI passthrough tests for consistency with Anthropic

- Schema tests for name, tool_calls, audio content, unknown fields
- Extractor tests for field preservation through applyMasked

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Co-authored-by: Stefan Gasser <redacted>