* fix: prevent empty reasoning messages in streaming interfaces
Prevents empty "Thinking..." indicators from appearing in clients by
filtering out reasoning messages with no content at the source.
Changes:
- Gemini: Don't emit ReasoningMessage when only thought_signature exists
- Gemini: Only emit reasoning content if text is non-empty
- Anthropic: Don't emit ReasoningMessage for BetaSignatureDelta
- Anthropic: Only emit reasoning content if thinking text is non-empty
This fixes the issue where providers send signature metadata before
actual thinking content, causing empty reasoning blocks to appear
in the UI after responses complete.
Affects: Gemini reasoning, Anthropic extended thinking
👾 Generated with [Letta Code](https://letta.com)
Co-Authored-By: Letta <noreply@letta.com>
* fix: handle Anthropic thinking signature correctly
- Only include 'signature' in Anthropic message payload if it is not None (fixes BadRequestError).
- Capture and attach 'signature' to ReasoningMessage in streaming interface.
* fix(anthropic): attach signature to last reasoning message in stream
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Co-authored-by: Letta <noreply@letta.com>
