fix:make reasoning effort configurable

[OneZero-Y]

What type of PR is this?

Fix - Resolves hardcoded values and improves configurability

What this PR does / why we need it:

This PR makes reasoning effort levels configurable instead of hardcoded, addressing a TODO comment in the codebase and improving system flexibility.
Changes:

1. Removes hardcoded reasoning effort: Previously hardcoded to "high", now configurable per category
2. Adds global default configuration: default_reasoning_effort in config.yaml for fallback behavior
3. Adds category-specific configuration: reasoning_effort field for fine-grained control per category
4. Maintains backward compatibility: Falls back to sensible defaults when configuration is missing
5. Updates function signatures: Enhanced setReasoningModeToRequestBody to accept category context

Configuration Examples:

# Global default
default_reasoning_effort: medium
# Category-specific settings  
categories:
- name: math
  reasoning_effort: high    # Math problems need intensive reasoning
- name: business  
  reasoning_effort: low     # Business conversations need light reasoning

Which issue(s) this PR fixes:

Fixes hardcoded reasoning effort levels (addresses TODO in reason_mode_selector.go:94)

Release Notes: Yes/No

[github-actions]

👥 vLLM Semantic Team Notification

The following members have been identified for the changed files in this PR and have been automatically assigned:

📁 config

Owners: @rootfs
Files changed:

• config/config.yaml

📁 src

Owners: @rootfs, @Xunzhuo, @wangchen615
Files changed:

• src/semantic-router/pkg/config/config.go
• src/semantic-router/pkg/extproc/reason_mode_config_test.go
• src/semantic-router/pkg/extproc/reason_mode_selector.go
• src/semantic-router/pkg/extproc/reasoning_integration_test.go
• src/semantic-router/pkg/extproc/request_handler.go

---

This comment was automatically generated based on the OWNER files in the repository.

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[rootfs]

@OneZero-Y can you run make test to fix the test failure?

The merge-base changed after approval.

[rootfs]

test failed

2025/09/02 12:50:29 No category determined for query, defaulting to no reasoning mode
--- FAIL: TestReasoningModeIntegration (0.00s)
    --- PASS: TestReasoningModeIntegration/Math_query_enables_reasoning (0.00s)
    --- PASS: TestReasoningModeIntegration/Business_query_disables_reasoning (0.00s)
    --- FAIL: TestReasoningModeIntegration/addReasoningModeToRequestBody_adds_correct_fields (0.00s)
    --- FAIL: TestReasoningModeIntegration/getChatTemplateKwargs_returns_correct_values (0.00s)
    --- PASS: TestReasoningModeIntegration/Empty_query_defaults_to_no_reasoning (0.00s)
    --- PASS: TestReasoningModeIntegration/Unknown_category_defaults_to_no_reasoning (0.00s)

[rootfs]

The config is currently manual, will have an automated process (to be listed in roadmap).
Test is green, merging now.

Thanks for contributing!