fix(llms): narrow _is_reasoning_model to not match gpt-5.x variants

[rudra717]

Linked Issue

Closes #4738

Description

_is_reasoning_model() used a substring match ("gpt-5" in model_lower) that incorrectly classified gpt-5.4-mini and other gpt-5.x variants as reasoning models. This caused temperature and other standard parameters to be silently stripped from API calls.

Root Cause

# Before — matches gpt-5, gpt-5o, BUT ALSO gpt-5.4-mini, gpt-5.4
if any(reasoning_model in model_lower for reasoning_model in ["gpt-5", "o1", "o3"]):
    return True

gpt-5.4-mini contains "gpt-5" as a substring, so it was misclassified. The _get_supported_params() method then stripped all parameters except messages, response_format, tools, and tool_choice — including temperature.

Fix

Replaced the broad substring match with:

• Exact match against known reasoning models (o1, o3, gpt-5, gpt-5o, etc.)
• Prefix match for dated variants (o1-2024-12-17, o3-2025-04-16)
• Provider prefix stripping (openai/o3-mini → o3-mini)
• Removed the "gpt-5" substring match entirely

Type of Change

• Bug fix (non-breaking change that fixes an issue)

Test Coverage

• I added/updated unit tests

Added 2 tests:

• test_gpt5_mini_not_classified_as_reasoning — verifies gpt-5.4-mini passes temperature through
• test_is_reasoning_model_classification — comprehensive classification test covering reasoning models (o1, o3, gpt-5, prefixed variants) and non-reasoning models (gpt-5.4-mini, gpt-5.4, gpt-4.1)

Checklist

• My code follows the project's style guidelines
• I have performed a self-review of my code
• I have added tests that prove my fix works
• New and existing tests pass locally
• I have updated documentation if needed

[CLAassistant]

All committers have signed the CLA.

[kartik-mem0]

please address the ci failing here

[rudra717]

Thanks @kartik-mem0, resolved the merge conflict kept both the upstream store tests from #4709 and the reasoning model classification tests from this PR. Also fixed the CI failure (missing mock_openai_client fixture on the classification test). should be green now