fix(ui): drawers close on any click outside the rail — TEST was the missing third

Creator: 'when the test slide-out is active, then any click off the div should
close the div — this behaviour applies to all tabs, not just TEST.'

MainWindow.Window_PreviewMouseLeftButtonDown already closed the Stream Settings
and YPP drawers on any click outside TextPullOutHost, but its close list skipped
TestSession — so the TEST drawer never dismissed on an outside click.

Fix: run TestSession.CloseDrawerCommand in the same outside-click branch.
All three drawers share the rail host, so the containment check is unchanged.

Good Dog: ONE integration test — the existing TestStream window section now
raises a window-root PreviewMouseLeftButtonDown (source = window => outside the
rail; deterministic, no OS mouse) and asserts the TEST and Stream Settings
drawers both close. Gate: clean build 0 warnings, full vstest 318/318.

ai.md

@@ -1559,7 +1559,10 @@ These are the hard facts behind every decision. Full list in `TASKS.md`.
   gold top bar + glow (`#9c6f1c`), a **TEST** badge, and the End button reads **"End Test"**;
   `StopStream` clears it in every path (including pump-failure rollback). Once the liveChatId
   resolves, `TestSession.BeginTest(broadcastId, liveChatId)` opens the **TEST drawer** (third
-  right-rail pull-out, three-way one-open-at-a-time exclusivity wired in `MainViewModel.Ypp.cs`).
+  right-rail pull-out, three-way one-open-at-a-time exclusivity wired in `MainViewModel.Ypp.cs`;
+  any left-click outside the rail closes whichever drawer is open — TEST included (fixed
+  2026-09-25, TASK 46; the code-behind outside-click close in `MainWindow` had skipped
+  TestSession, so only Stream Settings + YPP dismissed on an outside click).
   **liveChatId resolution (fixed 2026-09-25, TASK 44):** the id is `snippet.liveChatId` —
   `contentDetails` has NO liveChatId property — and YouTube only populates it once the broadcast
   is LIVE (the official GetLiveChatId.java sample lists broadcastStatus=active). So