fix: prevent "TextEditor is closed/disposed" warnings

[roomote]

This PR fixes the issue where "TextEditor is closed/disposed" warnings were being spammed in the logs when Roo Code performs API actions and edits documents.

Problem

The extension was attempting to access TextEditor instances that had already been disposed, causing frequent warning messages (tens per second) in the VS Code output.

Solution

• Added disposal tracking and checks to DecorationController before calling any TextEditor methods
• Added try-catch blocks around TextEditor property access to gracefully handle disposed editors
• Properly dispose decoration controllers in DiffViewProvider when resetting
• Protected editor access in getEnvironmentDetails.ts and registerCommands.ts
• Added comprehensive unit tests for disposal handling

Changes

• Modified DecorationController.ts to track disposal state and check editor validity before operations
• Updated DiffViewProvider.ts to properly dispose controllers and handle disposed editors
• Added protection in getEnvironmentDetails.ts for accessing editor document properties
• Added protection in registerCommands.ts for accessing editor viewColumn property
• Created comprehensive test suite for DecorationController disposal handling

Testing

• All existing tests pass
• New tests added specifically for disposal scenarios
• Verified that warnings no longer appear when editors are closed during operations

Fixes #5954

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Important

Fixes 'TextEditor is closed/disposed' warnings by adding disposal checks and handling in DecorationController and DiffViewProvider, with comprehensive tests added.

• Behavior:
  • Added disposal tracking and checks in DecorationController to prevent operations on disposed TextEditor instances.
  • Wrapped TextEditor property access in try-catch blocks in DecorationController.ts and DiffViewProvider.ts to handle disposed editors gracefully.
  • Properly dispose of decoration controllers in DiffViewProvider during reset.
  • Added checks in getEnvironmentDetails.ts and registerCommands.ts to protect against accessing properties of disposed editors.
• Testing:
  • Added comprehensive unit tests in __tests__/DecorationController.spec.ts to cover disposal scenarios.
  • Verified that warnings no longer appear when editors are closed during operations.
• Misc:
  • Minor logging changes to provide debug information when operations fail due to disposed editors.

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[daniel-lxs]

Closing in favor of #5958