The new windows-desktop CI job surfaced several tests that had never
actually run on Windows:
- SeparatorPenLifetimeTests expected Control.Disposed to fire only
once; current WinForms re-fires it on every Dispose() call.
- EditNestFocusTraversalTests assumed the Plates tab was selected by
default, which stopped being true once Drawings became the landing
tab; select it explicitly before asserting focus.
- NestReportExportTests asserted an exact plate count that ignored
PlateManager's trailing sentinel plate, and didn't expect the nest
name in the busy-export message.
- AtomicReportFileTests only expected IOException when replacing a
directory target; Windows raises UnauthorizedAccessException instead,
which callers already treat the same way.
Also register a ThreadException handler so an exception inside a
WndProc callback fails the test normally instead of popping a modal
dialog that blocks the desktop.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
