Fix PowerToys Run crashes when DWM desktop composition is disabled

[Copilot]

Summary of the Pull Request

PowerToys Run crashes with COMException: 已禁用桌面合成 (HRESULT 0x80263001 / DWM_E_COMPOSITIONDISABLED) in scenarios where DWM composition is temporarily or permanently unavailable (e.g. RDP sessions, compatibility modes). The existing recovery logic failed to catch DWM errors wrapped in WPF framework exception types.

ExceptionHelper.IsRecoverableDwmCompositionException

• Previously only inspected the outermost exception; WPF can wrap COMException inside other types
• Now walks the full exception chain up to 10 levels deep

ErrorReporting.HandleException

• Was passing e as COMException (→ null for non-COMException types) to a method whose signature takes Exception, making inner-exception detection a no-op
• Now passes e directly

ThemeManager.UpdateThemeWithRetryAsync

• catch (COMException ex) when (IsRecoverableDwmCompositionException(ex)) misses WPF wrapper types
• Changed to catch (Exception ex) when (...) — the when guard keeps semantics identical for non-DWM exceptions

MainWindow.OnSourceInitialized

• DwmSetWindowAttribute (rounded corners, Win11 only) was unprotected; a DWM failure here propagated to the global handler, disrupting window initialization
• Wrapped in try/catch — only consequence of failure is non-rounded corners (cosmetic)

PR Checklist

• Closes: #xxx
• Communication: I've discussed this with core contributors already. If the work hasn't been agreed, this work might be rejected
• Tests: Added/updated and all pass
• Localization: All end-user-facing strings can be localized
• Dev docs: Added/updated
• New binaries: Added on the required places
  • JSON for signing for new binaries
  • WXS for installer for new binaries and localization folder
  • YML for CI pipeline for new test projects
  • YML for signed pipeline
• Documentation updated: If checked, please file a pull request on our docs repo and link it here: #xxx

Detailed Description of the Pull Request / Additional comments

The core detection logic in IsRecoverableDwmCompositionException now walks the exception chain:

// Before: only checked if exception itself was COMException
if (exception is not COMException comException) return false;

// After: walk up to 10 inner exceptions
for (var depth = 0; current != null && depth < maxDepth; depth++, current = current.InnerException)
{
    if (current is COMException comException)
    {
        if (comException.HResult is DWM_E_COMPOSITIONDISABLED) return true;
        // ...
    }
}

The HandleException fix removes the redundant narrowing cast that prevented inner-exception detection from working even after this method was updated:

// Before (cast to null for non-COMException types):
if (ExceptionHelper.IsRecoverableDwmCompositionException(e as COMException))

// After:
if (ExceptionHelper.IsRecoverableDwmCompositionException(e))

Validation Steps Performed

• Code review of all affected exception handling paths
• Verified Exception.HResult is a public property in .NET (used consistently elsewhere in the codebase, e.g. ProgramLogger.cs, Log.cs)
• No new strings introduced; no binaries added

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