fix: resolve LM Studio context length detection (#5075)

[daniel-lxs]

Description

Fixes #5075

This PR resolves the issue where LM Studio models incorrectly show a context length of "1" instead of their actual context window size.

Changes Made

• Added fetchModel() method to LmStudioHandler that dynamically fetches model information from LM Studio using the existing getLMStudioModels() function
• Updated getModel() method to return actual model info with correct context length instead of static defaults
• Enhanced error handling with graceful fallback to default values when LM Studio is unavailable
• Added comprehensive tests covering successful fetching, error scenarios, and backward compatibility
• Maintained backward compatibility - existing functionality remains unchanged when fetching fails

Testing

• ✅ All existing tests pass (2457 tests passed, 47 skipped)
• ✅ New LM Studio-specific tests pass (12 tests passed)
• ✅ Manual testing completed:
  • Verified fetchModel() correctly calls getLMStudioModels()
  • Verified getModel() returns actual model info after fetching
  • Verified graceful error handling when LM Studio is unavailable
• ✅ Type checking passes
• ✅ Linting passes

Verification of Acceptance Criteria

• ✅ Context length detection: LM Studio models now show their actual context length instead of "1"
• ✅ No breaking changes: Maintains backward compatibility with graceful fallback
• ✅ Error handling: Properly handles cases where LM Studio is unavailable
• ✅ Test coverage: Comprehensive tests ensure the fix works correctly

Technical Details

Root Cause: The LmStudioHandler.getModel() method was returning openAiModelInfoSaneDefaults (which has contextWindow: 1) instead of fetching actual model information from LM Studio.

Solution: The handler now dynamically fetches model information using the existing getLMStudioModels() function, which correctly parses the actual context length from LM Studio's model metadata.

Implementation Pattern: Follows the same pattern used by other providers (OpenRouter, Requesty) that implement a fetchModel() method for dynamic model information retrieval.

Files Changed

• src/api/providers/lm-studio.ts - Added dynamic model fetching capability
• src/api/providers/__tests__/lmstudio.spec.ts - Updated tests to cover new functionality

Checklist

• Code follows project style guidelines
• Self-review completed
• Comments added for complex logic
• No breaking changes
• All tests pass
• Type checking passes
• Linting passes
• Issue requirements fully addressed

---

Important

Fixes context length detection in LmStudioHandler by dynamically fetching model info and enhancing error handling.

• Behavior:
  • LmStudioHandler now dynamically fetches model info using fetchModel() and getLMStudioModels().
  • getModel() returns actual model info with correct context length.
  • Graceful fallback to default values when LM Studio is unavailable.
• Testing:
  • Added tests in lmstudio.spec.ts for successful fetching, error scenarios, and backward compatibility.
  • Manual testing verified fetchModel() and getModel() behavior.
• Files Changed:
  • lm-studio.ts: Added dynamic model fetching and error handling.
  • lmstudio.spec.ts: Updated tests to cover new functionality.

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[delve-auditor]

✅ No security or compliance issues detected. Reviewed everything up to ac85aa6.

Security Overview

• 🔎 Scanned files: 2 changed file(s)

Detected Code Changes

Change Type	Relevant files
Bug Fix	► lmstudio.spec.ts     Add comprehensive tests for LM Studio model info fetching ► lm-studio.ts     Add fetchModel() method for dynamic model info     Update getModel() to return actual context length

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