Stabilize UIA modal waits in Windows live gate

[coneilen]

Summary

• Identified a pre-existing intermittent Windows UIA live-gate race: asynchronous New Loop commands sometimes timed out before the native Create or edit node modal appeared, or before a previous modal had fully closed.
• Replaced short fixed polling around the project-row, empty-global, and empty-project New Loop flows with named deadline-based waits for the expected modal and for modal closure.
• Added timeout diagnostics (UIA_WAIT_DIAGNOSTICS) and a validation-runner regression contract so future edits cannot silently reintroduce the short fixed New Loop polls.

RED: gh run view 35644468673 --repo scgopi/GraphCode --log-failed -> project-row New Loop did not open the node form after unit tests passed.
GREEN: pwsh -NoProfile -File .\Tools\windows\Tests\ValidationRunner.Tests.ps1 -> ValidationRunner.Tests.ps1: PASS.
REGRESSION: pwsh -NoProfile -File .\Tools\windows\Tests\WindowsShell.Tests.ps1 -> blocked locally by Zig 0.16 vs CI-pinned 0.15.2; GitHub Actions runs pinned validation.

Flake evidence

• gh run view 35626839265 --repo scgopi/GraphCode --log-failed -> Windows: dark-theme legacy dialogs and add loop-type teaching tiles #401 branch windows-shell failed with project-row New Loop did not open the node form. Run: https://github.com/scgopi/GraphCode/actions/runs/35626839265/job/106432664750
• gh run view 35631354431 --repo scgopi/GraphCode --log-failed -> same Windows: dark-theme legacy dialogs and add loop-type teaching tiles #401 branch windows-shell failure: project-row New Loop did not open the node form. Run: https://github.com/scgopi/GraphCode/actions/runs/35631354431/job/106442790808
• gh run view 35644468673 --repo scgopi/GraphCode --log-failed -> failed in windows-shell after All 95 tests passed; log ends with project-row New Loop did not open the node form. Run: https://github.com/scgopi/GraphCode/actions/runs/35644468673/job/106489093830
• gh run view 35634399529 --repo scgopi/GraphCode --log-failed -> failed on the same Windows: dark-theme legacy dialogs and add loop-type teaching tiles #401 branch with empty global New Loop did not open the node form. Run: https://github.com/scgopi/GraphCode/actions/runs/35634399529/job/106471257007
• gh run view 35634399525 --repo scgopi/GraphCode --log-failed -> failed in Windows validation after All 92 tests passed; diagnostics show foreground/focus on the CI zmx console, then empty global New Loop did not open the node form. Run: https://github.com/scgopi/GraphCode/actions/runs/35634399525
• gh run view 35633949744 --repo scgopi/GraphCode --log-failed -> unrelated branch failed in the same live gate at workspace right panel omitted collapse control, then self-healed in runs 35635440902 and 35638849754 without a targeted change. Run: https://github.com/scgopi/GraphCode/actions/runs/35633949744/job/106446641148
• gh run view 35638849754 --repo scgopi/GraphCode --json conclusion,url -> success for the same Windows shell validation workflow on a nearby sibling branch/rerun window. Run: https://github.com/scgopi/GraphCode/actions/runs/35638849754

RED

RED: gh run view 35644468673 --repo scgopi/GraphCode --log-failed -> repeated/superseded Windows UIA gate failure at project-row New Loop did not open the node form after unit tests had passed.

• gh run view 35634399525 --repo scgopi/GraphCode --log-failed -> independent Windows UIA gate failure at empty global New Loop did not open the node form, with focus diagnostics showing the runner/zmx console still foregrounded.

GREEN

GREEN: pwsh -NoProfile -File .\Tools\windows\Tests\ValidationRunner.Tests.ps1 -> ValidationRunner.Tests.ps1: PASS.

• PowerShell Parser.ParseFile(.\Tools\windows\uia-live-gate.ps1) -> uia-live-gate parser OK.

REGRESSION

REGRESSION: pwsh -NoProfile -File .\Tools\windows\Tests\WindowsShell.Tests.ps1 -> blocked locally before exercising this change because the host only has Zig 0.16.0, while the repo/CI pins Zig 0.15.2; failure is the expected stdlib API mismatch (GeneralPurposeAllocator, trimLeft, std.fs.cwd, etc.). Pinned live validation is left to GitHub Actions.

Notes

• This does not depend on or touch Windows: dark-theme legacy dialogs and add loop-type teaching tiles #401 rendering/font/AA changes.
• Coverage is preserved: the gate still requires each New Loop command to open the native node form and now also requires cancellation to close it before continuing.