Fix: Escape HTML special characters to prevent VSCode crash on Windows

[roomote]

Fixes #6041

This PR implements HTML escaping for all messages sent to the webview to prevent special characters from breaking the webview parser and crashing VSCode on Windows.

Problem

VSCode crashes on Windows when the Roo Code extension attempts to display apply_diff content containing special characters like <<<<<<< SEARCH. These characters are not properly escaped before being sent to the webview.

Solution

• Created HTML escaping utility (src/utils/htmlEscape.ts)
• Applied escaping to all ClineMessage content in ClineProvider and Task
• Added comprehensive tests for the escaping functionality

Testing

• All new tests pass (15/15)
• Existing tests continue to pass
• The specific crash scenario with apply_diff markers is now handled correctly

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Important

Implement HTML escaping for webview messages to prevent VSCode crashes on Windows due to unescaped special characters.

• Behavior:
  • Implement HTML escaping for all messages sent to the webview to prevent VSCode crashes on Windows.
  • Escape applied to ClineMessage content in Task and ClineProvider.
• Utilities:
  • New utility functions escapeHtml, escapeHtmlInObject, and escapeClineMessage in htmlEscape.ts.
• Testing:
  • Added tests in htmlEscape.spec.ts to verify escaping functionality for various cases, including special characters and diff markers.

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