fix: put Mount next in the automation row, gated to the Queued view

The button was parented to the dewar tab but never added to a layout, so
Qt painted it at (0, 0) over the TELL sample changer banner. It now sits
left of Unmount in the automation row (docked and pop-out), greyed out
outside the Queued view like Remove/Clear. A trailing stretch keeps the
row's buttons at their natural width instead of sharing the spare space.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

src/aare/gui/main_window.py

@@ -597,21 +597,27 @@ class MainWindow(QMainWindow):
         self.quick_unmount_button = QPushButton("⏏ Unmount", dewar_tab)
         self.quick_unmount_button.clicked.connect(lambda: self._on_manual_unmount_requested())
 
-        # main_window.py, next to quick_unmount_button (~L597)
+        # Was parented to dewar_tab but never added to a layout, so Qt
+        # painted it at (0, 0) — on top of the TELL banner. It lives in the
+        # automation row, left of Unmount, like the pop-out clone below.
         self.mount_next_button = QPushButton("⏭ Mount next", dewar_tab)
         self.mount_next_button.clicked.connect(self._mount_next_from_queue)
-        # add to automation_row loop + self._queue_action_buttons as kind "next"
 
         automation_row = QHBoxLayout()
         for w in (
             self.job_list_panel.play_button,
             self.job_list_panel.remove_button,
             self.job_list_panel.clear_button,
+            self.mount_next_button,
             self.quick_unmount_button,
             self.job_list_panel.park_and_dry_when_cleared,
             self.job_list_panel.pause_on_conditions_cb,
         ):
             automation_row.addWidget(w)
+        # Trailing stretch: without it every widget shares the spare width
+        # and the buttons balloon; five buttons plus two long checkboxes need
+        # them at their natural size.
+        automation_row.addStretch(1)
         dewar_layout.addLayout(automation_row)
 
         # "Remove selected" now unqueues the dewar-table selection — the
@@ -630,6 +636,7 @@ class MainWindow(QMainWindow):
             (self.job_list_panel.play_button, "run"),
             (self.job_list_panel.remove_button, "queue"),
             (self.job_list_panel.clear_button, "queue"),
+            (self.mount_next_button, "queue"),
         ]
         self.tell_samples.status_chips.buttonClicked.connect(
             lambda _chip: self._update_queue_buttons_enabled()
@@ -1462,19 +1469,22 @@ class MainWindow(QMainWindow):
         remove_button.clicked.connect(lambda: self._unqueue_panel_selection(dewar_panel))
         clear_button = QPushButton("✖ Clear list")
         clear_button.clicked.connect(jl.clear)
+        mount_next_button = QPushButton("⏭ Mount next")
+        mount_next_button.clicked.connect(self._mount_next_from_queue)
         unmount_button = QPushButton("⏏ Unmount")
         unmount_button.clicked.connect(lambda: self._on_manual_unmount_requested())
 
-        # Same Queued-view gating as the docked trio.
+        # Same Queued-view gating as the docked buttons.
         self._queue_action_buttons += [
             (run_button, "run"),
             (remove_button, "queue"),
             (clear_button, "queue"),
+            (mount_next_button, "queue"),
         ]
         self._update_queue_buttons_enabled()
 
         row = QHBoxLayout()
-        for button in (run_button, remove_button, clear_button, unmount_button):
+        for button in (run_button, remove_button, clear_button, mount_next_button, unmount_button):
             row.addWidget(button)
         for source in (jl.park_and_dry_when_cleared, jl.pause_on_conditions_cb):
             clone = QCheckBox(source.text())
@@ -1485,6 +1495,7 @@ class MainWindow(QMainWindow):
             clone.toggled.connect(source.setChecked)
             source.toggled.connect(clone.setChecked)
             row.addWidget(clone)
+        row.addStretch(1)  # natural button widths, see the docked row
         return row
 
     def _show_admin_tip(self, message: str) -> None: