docs: record the modal that hangs test_mainwindow as item 84

Cause verified by attaching gdb to the hung process rather than
inferred: showWarnings() raises QMessageBox::warning from the MainWindow
constructor, and nothing offscreen can dismiss it, so any config problem
in a test's fixture blocks the constructor forever.

Not a defect in the application. The modal is right for a person and the
code says why; the defect is that a test cannot dismiss it and the
resulting failure is a silent hang rather than an error naming the
cause.

Corrects item 81's closing note, which blamed the missing maildir key
itself.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

1 files changed, 5 insertions, 3 deletions

diff --git a/docs/superpowers/plans/2026-08-03-post-0.1.0-usability-closed.md b/docs/superpowers/plans/2026-08-03-post-0.1.0-usability-closed.md
index 50dd8ee..8cfa6b0 100644
--- a/docs/superpowers/plans/2026-08-03-post-0.1.0-usability-closed.md
+++ b/docs/superpowers/plans/2026-08-03-post-0.1.0-usability-closed.md
@@ -4736,6 +4736,8 @@ A third surfaced while testing. A generated saved query that resolves to an
 EMPTY query is skipped when the row is built (`src/mainwindow.cpp:1692`), so a
 test asserting that Sent offers no rule action passed by finding no Sent button
 at all. It needs a configured account with a sent folder to assert anything.
-An account section missing `maildir` does not merely fail, it HANGS
-`test_mainwindow` outright, which is how this was found: the suite ran past
-its two-minute timeout with no output.
+An account section missing `maildir` HANGS `test_mainwindow` outright, which is
+how this was found: the suite ran past its two-minute timeout with no output.
+The cause is not the account at all, it is `showWarnings()` raising a modal
+from the MainWindow constructor for any config problem, with nothing offscreen
+to dismiss it. Filed as item 84.