fix(provider): add missing index field to streaming tool_call deltas (#6661) (#6692)

* fix(provider): add missing index field to streaming tool_call deltas

- Fix #6661: Streaming tool_call arguments lost when OpenAI-compatible proxy omits index field
- Gemini and some proxies (e.g. Continue) don't include index field in tool_call deltas
- Add default index=0 when missing to prevent ChatCompletionStreamState.handle_chunk() from rejecting chunks

Fixes #6661

* fix(provider): use enumerate for multi-tool-call index assignment

- Use enumerate() to assign correct index based on list position
- Iterate over all choices (not just the first) for completeness
- Addresses review feedback from sourcery-ai and gemini-code-assist

---------

Co-authored-by: Yaohua-Leo <3067173925@qq.com>
Co-authored-by: Soulter <905617992@qq.com>

astrbot/core/provider/sources/openai_source.py

@@ -334,11 +334,15 @@ class ProviderOpenAIOfficial(Provider):
             choice = chunk.choices[0]
             delta = choice.delta
 
-            # siliconflow workaround
             if dtcs := delta.tool_calls:
-                for tc in dtcs:
+                for idx, tc in enumerate(dtcs):
+                    # siliconflow workaround
                     if tc.function and tc.function.arguments:
                         tc.type = "function"
+                    # Fix for #6661: Add missing 'index' field to tool_call deltas
+                    # Gemini and some OpenAI-compatible proxies omit this field
+                    if not hasattr(tc, "index") or tc.index is None:
+                        tc.index = idx
             try:
                 state.handle_chunk(chunk)
             except Exception as e: