fix: add includeVSCodeFileContext setting to control VSCode file context in API calls

[roomote]

This PR fixes issue #6194 where excessive VSCode file context was causing connection errors with LLMs that have limited context windows.

Changes

• Added new global setting includeVSCodeFileContext (defaults to true for backward compatibility)
• Updated getEnvironmentDetails to conditionally include VSCode file context based on the setting
• Added setting to ExtensionState and webview message handler
• Added comprehensive tests for the new functionality
• Updated webview-ui components to include the new property

How it works

When includeVSCodeFileContext is set to false, the VSCode visible files and open tabs sections will not be included in subsequent API calls after the initial request. This significantly reduces the context size for models with limited context windows.

The setting defaults to true to maintain backward compatibility for users who rely on the current behavior.

Fixes #6194

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Important

Introduces includeVSCodeFileContext setting to manage VSCode file context inclusion in API calls, with updates to settings, tests, and UI components.

• Behavior:
  • Adds includeVSCodeFileContext setting to control inclusion of VSCode file context in API calls, defaulting to true.
  • Updates getEnvironmentDetails in getEnvironmentDetails.ts to conditionally include VSCode file context.
  • Modifies webviewMessageHandler in webviewMessageHandler.ts to handle includeVSCodeFileContext messages.
• Tests:
  • Adds tests in getEnvironmentDetails.spec.ts and ClineProvider.spec.ts to verify behavior when includeVSCodeFileContext is toggled.
• UI:
  • Updates ExtensionStateContext.tsx and ExtensionStateContext.spec.tsx to manage and test the new setting.

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