Fix Copilot review feedback for PowerShell dev actions

[Copilot]

Addresses the linked review comments for PR #2849 around TypeScript conformance and abort-cancellation safety in the Copilot dev-action path.

• PowerShell tests

  • Removed the duplicate itOnWindows declaration that caused a block-scoped redeclaration error.

• ClientIO compatibility

  • Updated the Copilot plugin’s question implementation to match ClientIO.question, including the optional source parameter.

• Abort cancellation

  • Made cancelCommandByClientId best-effort when aborting before a request id is available.
  • Added coverage for synchronous cancellation failures so abort handlers do not throw.

try {
    dispatcher.cancelCommandByClientId(clientRequestId);
    earlyCancellation = Promise.resolve();
} catch (error) {
    earlyCancellation = Promise.reject(error);
}