feat(desktop): the mouse back button steps out of the drawer

The side button (BTN_SIDE, Qt.BackButton) does what Escape does: closes
the history, then leaves a page for the tiles, then closes the drawer.
Both go through one back(). The first attempt let the press fall through
to the full-surface click catcher under the panel, since nothing above
it accepts that button; it never arrived while a page was open. A
MouseArea on top with z: 1, taking only the back button, works, and
left clicks still pass through it.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

1 files changed, 5 insertions, 0 deletions

diff --git a/AGENTS.md b/AGENTS.md
index 9b809ea..48f7970 100644
--- a/AGENTS.md
+++ b/AGENTS.md
@@ -138,6 +138,11 @@ changing that component. The ones that generalise:
   The pills lose the pointer, so the hide timer would close the island under
   the open menu. `display()` reports no close, so the island holds itself shown
   after it until the pointer returns (a ponytail ceiling in `Island.qml`).
+- **A mouse button nothing accepts does not reliably fall through to a
+  catcher underneath.** The drawer's back button (`BTN_SIDE`, `Qt.BackButton`)
+  never reached a full-surface `MouseArea` below the panel while a page was
+  open. A `MouseArea` on top with `z: 1` and `acceptedButtons: Qt.BackButton`
+  works, and left clicks still pass through it to the items below.
 - **A `WheelHandler` on an `Image` inside the island's status pill never
   fired**; `MouseArea { onWheel }` in the same place works, and `SoundPage`
   already used it. Prefer `MouseArea.onWheel`.