Add comprehensive tests for lm/utils.ts chatCommand function

[Copilot]

This PR adds missing test coverage for the chatCommand() function in src/lm/utils.ts. The function determines which chat command to use based on the experimental.useQuickChat configuration setting, but was previously untested.

Changes Made

• Created src/test/lm/utils.test.ts with comprehensive test coverage
• Added tests for all code paths:
  • Returns QUICK_CHAT_OPEN when experimental.useQuickChat is true
  • Returns OPEN_CHAT when experimental.useQuickChat is false
  • Returns OPEN_CHAT when using the default value (undefined/false)

Implementation Details

The tests use proper VS Code workspace configuration mocking to simulate different user settings. Each test case:

1. Mocks vscode.workspace.getConfiguration() to return controlled values
2. Calls the chatCommand() function
3. Verifies the correct command constant is returned
4. Properly cleans up mocks using beforeEach/afterEach hooks

The implementation follows existing project patterns and passes all linting, hygiene, and TypeScript compilation checks.

Why This Matters

Having test coverage for this utility function ensures that:

• Changes to the chat command selection logic are validated
• The experimental feature flag behavior is properly tested
• Regression testing prevents breaking the chat integration functionality

This addresses the gap in test coverage for language model utilities and helps maintain code quality standards across the extension.

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  • Triggering command: /opt/hostedtoolcache/node/20.19.4/x64/bin/node ./out/src/test/runTests.js --help (dns block)

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