[Shortcut Guide] Prevent overlay crash on section navigation (#48448)

[niels9001]

Summary of the Pull Request

Shortcut Guide overlay crashes and closes when navigating between sidebar sections (e.g. clicking PowerToys, then clicking the Windows icon to come back). Repro and crash logs in #48448. Crash logs in #48441 show the same propagation path plus a follow-up access violation in coreclr, indicating exceptions that escape local catches.

This PR fixes the immediate navigation race and adds broader crash hardening so future exceptions on the UI/background threads are logged instead of tearing down the overlay.

Navigation-race fix (commit 1)

Root cause: WindowSelector_SelectionChanged calls App.TaskBarWindow.Activate() and then SetWindowPosition() synchronously. Activate() runs a reentrant Window_Activated → BringToFront → TaskbarWindow.Activated chain that can leave App.TaskBarWindow.AppWindow momentarily null, so SetWindowPosition throws NullReferenceException.

Because the initial SelectedItem = MenuItems[0] is set from SetNavItems, the NRE bubbles up into InitializeNavItemsAsync's catch block — which sets _closeType = "InitializationFailed" and closes the window. That matches both user-visible symptoms: the overlay "flashes and disappears" (#48441) on open and "closes when clicking the Windows icon" (#48448).

Edits in src/modules/ShortcutGuide/ShortcutGuide.Ui/ShortcutGuideXAML/MainWindow.xaml.cs:

• SetWindowPosition: null-guard App.TaskBarWindow?.AppWindow and skip the taskbar-overlap height adjustment when it is not currently observable. Wrap the body in try/catch with Logger.LogError so any future positioning hiccup keeps the previous layout instead of taking down the overlay.
• WindowSelector_SelectionChanged: null-guard App.TaskBarWindow?.Hide() / Activate() and wrap the body in try/catch. This breaks the propagation path that lets a navigation exception reach InitializeNavItemsAsync's "fatal init failure" branch.

Crash hardening (commit 2)

Additional defensive changes to cover other unguarded paths surfaced while reviewing #48441:

• App.xaml.cs: register App.UnhandledException, AppDomain.CurrentDomain.UnhandledException, and TaskScheduler.UnobservedTaskException so a stray exception (e.g. an IO failure during a fire-and-forget UI handler, or a background Task fault) gets logged instead of tearing the process down with an access violation in coreclr. Mirrors what Peek, AdvancedPaste, and CmdPal already do.
• App.OnLaunched: wrap the launch sequence in try/catch and exit cleanly with an error log on failure (LoadData / MainWindow / TaskbarWindow ctors and Activate are all reachable failure points).
• App.LoadData: broaden the Pinned.json deserialize catch to also handle IOException / UnauthorizedAccessException, and guard the round-trip SaveSettings call as best-effort with a warning log.
• PinnedShortcutsHelper.Save: catch IOException / UnauthorizedAccessException / JsonException and log; Pin / Unpin runs from a synchronous UI handler so an unguarded File.WriteAllText would tear down the overlay on any disk hiccup.
• TaskbarWindow.UpdateTasklistButtons: move the AppWindow.Move calls inside the existing try block, null-guard App.MainWindow?.AppWindow up front, and wrap the whole body so the method (which runs from the ctor and from Activated) cannot tear the overlay down when MainWindow is in a transient state.

PR Checklist

• Closes: Shortcut Guide crashes when clicking the Windows icon after navigating to another section #48448
• Likely also fixes: The new Shortcut guide does not work, and even if it did I preferred the older one. #48441
• Communication: Defensive fix to known crash paths; no API change.
• Tests: No automated tests added — the failures are reentrancy / timing races that are hard to deterministically trigger in CI. Validated with a synthetic repro (see below).
• Localization: N/A — only logger strings.
• Dev docs: N/A
• New binaries: N/A

Detailed Description of the Pull Request / Additional comments

The fix is intentionally defensive (rather than restructuring the reentrant activation flow) because the legacy taskbar UIA enumeration (TasklistPositions.GetButtons) on Windows 10 is what most reliably widens the race window and is out of scope to redesign for a hotfix.

Validation Steps Performed

• Build: tools\build\build.cmd from src\modules\ShortcutGuide\ShortcutGuide.Ui — exit 0, errors log empty for both commits.
• Synthetic repro: temporarily injected throw new NullReferenceException() at the top of SetWindowPosition to exercise the exact propagation path the reporter's log shows (SetWindowPosition → SelectionChanged → set_SelectedItem → InitializeNavItemsAsync.catch → Close("InitializationFailed")).
  • Before fix: overlay flashes and closes, log shows Failed to initialize navigation items. with the NRE.
  • After fix: overlay stays open, page navigates, log shows Failed to set Shortcut Guide window position; keeping previous layout. from the new catch.
• Did not reproduce the live race on a Win11 dev box; the reporter's repro is Windows 10 19045 / Microsoft Store install where the legacy taskbar UIA timing makes the reentrant chain more likely to expose the null.

[Copilot]

Pull request overview

This PR hardens the Shortcut Guide overlay against a reentrancy-related crash when navigating between sidebar sections by preventing exceptions in the selection-change/positioning path from propagating into initialization failure logic.

Changes:

• Wraps SetWindowPosition() in a try/catch and skips taskbar overlap calculations when App.TaskBarWindow.AppWindow is temporarily unavailable.
• Wraps WindowSelector_SelectionChanged in a try/catch and adds null-guards around taskbar window interactions to avoid closing the overlay on navigation-time exceptions.
• Adds new error logging for both the positioning and section-selection failure paths.

[github-actions]

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