new_gui: adopt backend-mounted sample on restart (status.sample sync)

Mount state was GUI-local, so a restart 'forgot' a physically-mounted sample.
_on_status now syncs from status.sample: adopt it when the GUI is empty or shows
a different sample (no robot mount), with a guard (_last_unmount_id) so a just-
unmounted sample isn't re-adopted from a stale poll. AppState.sync_mounted.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

src/aare/gui/new_gui/main_window.py

@@ -89,6 +89,10 @@ class MainWindow(QWidget):
         self._baton_poll.setInterval(1000)
         self._baton_poll.timeout.connect(self._poll_baton_timeout)
 
+        # mounted-sample sync with the backend (status.sample)
+        self._mounted_db_id = None        # what the GUI currently shows mounted
+        self._last_unmount_id = None      # suppress re-adopting a just-unmounted one
+
         # last payloads cached so a live theme rebuild can re-feed the new views
         self._last_status = None
         self._last_spreadsheet = None
@@ -231,6 +235,7 @@ class MainWindow(QWidget):
         s = self.state
         s.mode_changed.connect(self._on_mode_changed)
         s.mount_requested.connect(self._on_mount_requested)
+        s.unmount_requested.connect(self._on_unmount_note)
         s.unmount_requested.connect(self.daq.unmount)
 
         self.daq.update.connect(self._on_status)
@@ -453,6 +458,26 @@ class MainWindow(QWidget):
         if self._precondition_ok():
             self.daq.fluorimeter_spectrum(req)
 
+    def _sync_mounted_from_status(self, s) -> None:
+        """Reflect the backend's mounted sample (status.sample) in the GUI, so a
+        restart (or an external mount) doesn't 'forget' a mounted sample."""
+        bs = getattr(s, "sample", None)
+        if bs is None:
+            self._last_unmount_id = None     # unmount confirmed by backend
+            return
+        bid = getattr(bs, "db_id", None)
+        if bid is not None and bid == self._last_unmount_id:
+            return                            # don't re-adopt a just-unmounted one
+        cur = self.state.mount_sample
+        cur_id = getattr(cur, "db_id", None) if cur is not None else None
+        if self.state.mount_phase != "mounted" or cur_id != bid:
+            self._mounted_db_id = bid
+            self.state.sync_mounted(bs)
+
+    def _on_unmount_note(self) -> None:
+        self._last_unmount_id = self._mounted_db_id
+        self._mounted_db_id = None
+
     @Slot(object, bool)
     def _on_mount_requested(self, sample, reference: bool = False) -> None:
         reason = preconditions.hutch_blocks_mount(self.manual.last_status)
@@ -460,6 +485,8 @@ class MainWindow(QWidget):
             QMessageBox.critical(self, "Mounting blocked", reason)
             self.alert.show_message(reason, "error")
             return
+        self._mounted_db_id = getattr(sample, "db_id", None)
+        self._last_unmount_id = None
         self.daq.mount(sample, reference)
 
     def _open_staff_tools(self) -> None:
@@ -530,6 +557,7 @@ class MainWindow(QWidget):
     def _on_status(self, s) -> None:
         self._last_status = s
         self._auto_busy_edge(s)
+        self._sync_mounted_from_status(s)
         session = getattr(s, "session", None)
         staff = bool(getattr(session, "staff", False)) if session else False
         if staff != self._staff:

src/aare/gui/new_gui/state.py

@@ -216,6 +216,18 @@ class AppState(QObject):
         self.mount_changed.emit()
         self.pipe_changed.emit()
 
+    def sync_mounted(self, sample) -> None:
+        """Adopt a sample the backend reports as mounted (e.g. on GUI restart).
+
+        Does NOT drive the robot — it only reflects reality. No mount_requested."""
+        self._mount_sample = sample
+        self._manual_mount = False
+        if self._mount_phase != "mounted":
+            self._reset_pipe()
+            self.pipe_changed.emit()
+        self._mount_phase = "mounted"
+        self.mount_changed.emit()
+
     def unmount(self) -> None:
         """mounted -> empty: clear sample. Robot unmount only for DB samples."""
         manual = getattr(self, "_manual_mount", False)