v0.5.0

• Native SSE streaming for Anthropic & OpenAI — the single-shot fallback is
  gone. Text/thinking deltas stream as partial chunks, tool-call arguments are
  reassembled across fragments, and the final chunk carries the stop reason and
  usage. All three providers now share one chunk contract.
• Multimodal input for Anthropic & OpenAI — inline images map to base64
  image blocks / data: URI image_url parts, inline PDFs to Anthropic
  document blocks, https:// file references to URL sources. Unsupported
  parts are dropped with a warning — never silently.
• Anthropic prompt caching — the same ContextCacheConfig that drives
  Gemini's explicit cache becomes a cache_control breakpoint on the system
  block (or last tool); ttl_seconds >= 3600 selects the 1-hour tier. Cache
  activity surfaces via cache_metadata and cached_content_token_count.
• Reasoning-model fix — max_output_tokens is sent as
  max_completion_tokens for o-series / gpt-5 models (which reject the
  deprecated max_tokens), keeping older OpenAI-compatible servers on the
  legacy field.
• examples/compat_check — live wire-compatibility smoke test against the
  real Anthropic and OpenAI APIs (generation, streaming, tools, structured
  output, images, caching). Run it with your keys; exits non-zero on failure.

Full Changelog: v0.4.0...v0.5.0