Stabilize UIA modal waits in Windows live gate (#402)

Replace the short fixed New Loop modal polling in the Windows UIA live gate with deadline-based waits for the expected modal window and for cancellation to fully close it before the next asynchronous command. The timeout path now emits UIA_WAIT_DIAGNOSTICS with foreground/focus state, preserving actionable failure output instead of hiding errors.

Add a validation-runner contract so the live gate keeps using deterministic modal waits around project-row, empty-global, and empty-project New Loop flows.

Signed-off-by: Colin Neilens <coneilen@microsoft.com>
Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Author: coneilen