feat: add Gemini SSE streaming response parsing

[NameHaibinZhang]

#2394

#1854

Implement parseGeminiStream() to handle Server-Sent Events responses from Gemini's streamGenerateContent endpoint. This adds streaming support comparable to what exists for OpenAI and Anthropic providers.

Changes:

• New gemini_stream.go with SSE parsing and text/functionCall aggregation
• Modified GeminiSpan() to dispatch between JSON and SSE responses
• Comprehensive test coverage for streaming scenarios

Summary

Describe the change briefly.

Validation

• I have read and followed the contributing guidelines
• If this enhances / fixes / changes a core feature, I have updated the features documentation and support matrix as needed.

[codecov]

Codecov Report

❌ Patch coverage is 68.42105% with 42 lines in your changes missing coverage. Please review.
✅ Project coverage is 69.35%. Comparing base (b9fe20e) to head (37a29b6).
⚠️ Report is 9 commits behind head on main.

Files with missing lines	Patch %	Lines
pkg/ebpf/common/http/gemini_stream.go	68.90%	32 Missing and 5 partials ⚠️
pkg/ebpf/common/http/gemini.go	64.28%	4 Missing and 1 partial ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2530      +/-   ##
==========================================
+ Coverage   69.07%   69.35%   +0.27%     
==========================================
  Files         348      349       +1     
  Lines       47314    47509     +195     
==========================================
+ Hits        32683    32950     +267     
+ Misses      12582    12503      -79     
- Partials     2049     2056       +7     

Flag	Coverage Δ
integration-test	51.43% <0.00%> (+0.56%)	⬆️
integration-test-arm	26.98% <0.00%> (+0.69%)	⬆️
integration-test-vm-5.15-lts	?
integration-test-vm-6.18-lts	?
k8s-integration-test	35.78% <0.00%> (-0.40%)	⬇️
oats-test	35.29% <2.88%> (-0.29%)	⬇️
unittests	63.71% <87.50%> (+0.16%)	⬆️

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[mariomac]

Looks good! Thanks for your contribution

[Copilot]

Pull request overview

Adds Gemini SSE (Server-Sent Events) streaming response parsing so Gemini spans can normalize output similarly to existing OpenAI/Anthropic streaming support.

Changes:

• Added parseGeminiStream() and helpers to aggregate streamed text and function-call tool names into a GeminiResponse.
• Updated GeminiSpan() to dispatch between JSON and SSE responses using looksLikeJSON().
• Added unit tests covering Gemini streaming parsing and span extraction for stream responses.

Reviewed changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated 2 comments.

File	Description
pkg/ebpf/common/http/gemini.go	Switches Gemini response parsing between JSON and SSE; wires tool-call extraction for both cases.
pkg/ebpf/common/http/gemini_stream.go	Implements SSE parsing + aggregation into a synthetic GeminiResponse plus tool calls.
pkg/ebpf/common/http/gemini_test.go	Adds a GeminiSpan streaming-response test to validate end-to-end extraction.
pkg/ebpf/common/http/gemini_stream_test.go	Adds focused unit tests for parseGeminiStream() (text aggregation, tool calls, empty/truncated streams).

[MrAlias]

Thanks for adding Gemini streaming support. The overall integration direction matches what we do for the other GenAI providers, but the stream parser is currently a bit too lossy for Gemini's response shape. I think we should tighten the parser and add coverage for those cases before merging.

[NameHaibinZhang]

done