Do not register protocol handler in portable mode

[Copilot]

When running in portable mode (VSCODE_PORTABLE env var set), the Windows protocol handler registration causes OAuth redirects to launch VS Code in non-portable mode, storing authentication tokens outside the portable directory.

Changes

• Added isPortable property to IEnvironmentMainService: Checks VSCODE_PORTABLE environment variable
• Modified ElectronURLListener: Skip app.setAsDefaultProtocolClient() on Windows when isPortable is true
• Added unit tests: Verify isPortable detection behavior

Impact

Protocol handler-based OAuth flows will fail in portable mode. Users can use the fallback local server OAuth method instead.

Original prompt

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This section details on the original issue you should resolve

<issue_title>Do not register a protocol handler in portable mode</issue_title>
<issue_description>

• Does this issue occur when all extensions are disabled?: Yes

• VS Code Version: 1.96.4
• OS Version: x64 10.0.19045

Steps to Reproduce:

1. Run VS Code in portable mode (set VSCODE_PORTABLE env var to a custom path).
2. View Computer\HKEY_CLASSES_ROOT\vscode. Observe that the configured command in shell\open\command does not preserve portable mode.
3. Alternatively, try authenticating with GitHub (or another service that uses OAuth with the protocol handler). Observe that after you authenticate in your browser, VS Code is launched in non-portable mode (so that auth token will not be stored in the portable config).

Possible solutions:

1. Skip registering the protocol handler when portable mode is active. This means that authentication flows that rely on the protocol handler will fail (but the user can use the fallback oauth method by using a local server).
2. Store arguments and environment variables used to configure the main VS Code instance somewhere and when invoking VS Code again through a protocol handler, restore them, so that portable mode works properly. It would be courteous toward the user to remove the protocol handler when VS Code exits, so that it does not leave random garbage on the machine when running in portable mode.

The handler is installed here during VS Code startup:

vscode/src/vs/platform/url/electron-main/electronUrlListener.ts

Lines 52 to 55 in bda07cf

	if (isWindows) {
	const windowsParameters = environmentMainService.isBuilt ? [] : [`"${environmentMainService.appRoot}"`];
	windowsParameters.push('--open-url', '--');
	app.setAsDefaultProtocolClient(productService.urlProtocol, process.execPath, windowsParameters);

</issue_description>

Comments on the Issue (you are @copilot in this section)

• Fixes Do not register a protocol handler in portable mode #239139

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[dmitrivMS]

Will use new PR here 287063