v0.2.0

Added

• Provider prompt caching across all backends:
  • Anthropic: with_prompt_caching() now correctly injects cache_control blocks on the system message and the last tool definition, enabling actual cache hits. Parses cache_creation_input_tokens and cache_read_input_tokens from usage with tracing.
  • OpenAI: Parses prompt_tokens_details.cached_tokens from the usage response (automatic prompt caching).
  • Azure OpenAI: Same as OpenAI — parses prompt_tokens_details.cached_tokens.
  • Google Gemini: New with_cached_content(name) builder method to reference a cachedContents/<id> resource. Parses cachedContentTokenCount from usage metadata.
  • AWS Bedrock: New with_prompt_caching() builder inserts CachePoint blocks after system messages and tool definitions. Parses cache_read_input_tokens from the Converse API response.
  • Ollama: New with_keep_alive(duration) builder to control KV cache retention (e.g. "5m", "1h", "0").
• Usage::cached_tokens field — number of input tokens served from the provider's cache (subset of input_tokens, defaults to 0).

Fixed

• Anthropic caching was non-functional: the with_prompt_caching() flag sent the beta header but never added cache_control content blocks, so no caching actually occurred. Now correctly marks the system prompt and last tool definition as cache breakpoints.