* fix: handle Anthropic overloaded_error in streaming interfaces
* fix: handle Unicode surrogates in OpenAI requests
Sanitize Unicode surrogate pairs before sending requests to OpenAI API.
Surrogate pairs (U+D800-U+DFFF) are UTF-16 encoding artifacts that cause
UnicodeEncodeError when encoding to UTF-8.
Fixes Datadog error: 'utf-8' codec can't encode character '\ud83c' in
position 326605: surrogates not allowed
* fix: handle UnicodeEncodeError from lone Unicode surrogates in OpenAI requests
Improved sanitize_unicode_surrogates() to explicitly filter out lone
surrogate characters (U+D800 to U+DFFF) which are invalid in UTF-8.
Previous implementation used errors='ignore' which could still fail in
edge cases. New approach directly checks Unicode code points and removes
any surrogates before data reaches httpx encoding.
Also added sanitization to stream_async_responses() method which was
missing it.
Fixes: 'utf-8' codec can't encode character '\ud83c' in position X:
surrogates not allowed
6f746c5225