Disable double-click to reveal source for .copilotmd files in markdown preview

[Copilot]

This PR disables the double-click behavior that reveals markdown source for files with the .copilotmd extension, while preserving all existing functionality for regular .md files.

Problem

Currently, double-clicking in the markdown preview reveals the source markdown for all markdown files. For .copilotmd files, this behavior should be disabled to prevent users from accidentally switching to the source view.

Solution

Added a file extension check in the double-click event listener in extensions/markdown-language-features/preview-src/index.ts. The implementation:

1. Checks if the current document resource ends with .copilotmd
2. Returns early if it's a copilotmd file, preventing the double-click action
3. Preserves all existing behavior for regular markdown files

document.addEventListener('dblclick', event => {
    if (!settings.settings.doubleClickToSwitchToEditor) {
        return;
    }

    // Disable double-click to switch editor for .copilotmd files
    if (documentResource && documentResource.endsWith('.copilotmd')) {
        return;
    }

    // ... rest of existing logic unchanged
});

Impact

• ✅ .copilotmd files: Double-click no longer reveals markdown source
• ✅ .md files: Double-click behavior unchanged (still reveals source)
• ✅ All other markdown preview features remain fully functional (links, scrolling, rendering)

This is a minimal, surgical change that addresses the specific requirement without affecting existing functionality.

This pull request was created as a result of the following prompt from Copilot chat.

The current behavior in CopilotMD files allows users to double-click and reveal the Markdown source. We want to disable this specific double-click behavior in files with the .copilotmd extension, so double-clicking does not reveal the Markdown source. All other Markdown editing behaviors should remain unaffected for non-copilotmd files.

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[Copilot]

Pull Request Overview

This PR disables the double-click to reveal source functionality specifically for .copilotmd files in the markdown preview, while preserving the existing behavior for regular .md files.

• Adds a file extension check to prevent double-click source reveal for .copilotmd files
• Maintains all existing double-click behavior for standard markdown files
• Uses early return pattern to exit the event handler when dealing with copilotmd files

[joaomoreno]

Ugly fix but OK...

[TylerLeonhardt]

Does this work in Copilot Instuctions files which have the Language Type of "Instructions" and not "Markdown"?

[joaomoreno]

It only works if the file has file extension .copilotmd.