fix: omit temperature parameter when not explicitly set for OpenAI Compatible providers

[ghost]

Summary

This PR fixes an issue where the temperature parameter was always being sent with a value of 0.0 when "Use custom temperature" was unchecked in the OpenAI Compatible provider settings. This prevented backend services (like LiteLLM/vLLM) from using their configured default temperatures.

Problem

When configuring RooCode with an OpenAI Compatible Provider pointing at a LocalLLM (LiteLLM → vLLM stack):

• If "Use custom temperature" was unchecked, all requests were sent with temperature: 0.0 (greedy decoding)
• This overrode any backend-configured defaults (e.g., LiteLLM's configured temperature)
• Users expected that unchecking the option would allow the backend to use its own defaults

Solution

Modified the temperature handling in two key places:

1. OpenAiHandler - Only includes temperature in the request when modelTemperature is explicitly defined
2. BaseOpenAiCompatibleProvider - Only includes temperature when modelTemperature is explicitly defined

Special case: DeepSeek Reasoner models still get their specific default temperature when not explicitly set.

Changes

• Modified src/api/providers/openai.ts to conditionally include temperature
• Modified src/api/providers/base-openai-compatible-provider.ts to conditionally include temperature
• Added comprehensive tests to verify the new behavior
• Updated existing tests that were expecting temperature to always be present

Testing

• ✅ Added tests to verify temperature is omitted when undefined
• ✅ Added tests to verify temperature is included when explicitly set (including 0)
• ✅ Updated existing tests to work with the new behavior
• ✅ All tests passing

Fixes #7187

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Important

Fixes temperature parameter handling in OpenAI Compatible providers to only include it when explicitly set, allowing backend defaults to be used.

• Behavior:
  • OpenAiHandler and BaseOpenAiCompatibleProvider now only include temperature in requests if modelTemperature is explicitly set.
  • Special case for DeepSeek Reasoner models to use a specific default temperature when not set.
• Code Changes:
  • Modified src/api/providers/openai.ts and src/api/providers/base-openai-compatible-provider.ts to conditionally include temperature.
• Testing:
  • Added tests to verify temperature is omitted when undefined and included when set in openai.spec.ts, groq.spec.ts, and other test files.
  • Updated existing tests to align with new behavior.
  • All tests passing.

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[ghost]

I reviewed my own code and found it surprisingly tolerable. Almost like I knew what I was doing.

[ghost]

Is this intentional? The temperature is set inline here (line 119) while in other tests it's part of the options object. Could we standardize this for better consistency?

[ghost]

The special handling for DeepSeek Reasoner models is well-implemented. Could we add a comment explaining why this model requires a specific default temperature? This would help future maintainers understand the reasoning behind this special case.

[daniel-lxs]

I wonder if we don't need to send this anymore since we are letting the provider set it