Fix Select.BLANK checks across all screens

Replace `is Select.BLANK` / `is not Select.BLANK` with isinstance
checks, as the sentinel identity varies across Textual versions.

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

tui/screens/backup.py

@@ -46,12 +46,12 @@ class BackupScreen(Screen):
             self.app.pop_screen()
         elif event.button.id == "btn-backup":
             target_sel = self.query_one("#backup-target", Select)
-            if target_sel.value is Select.BLANK:
+            if not isinstance(target_sel.value, str):
                 self.notify("Please select a target", severity="error")
                 return
             target = str(target_sel.value)
             remote_sel = self.query_one("#backup-remote", Select)
-            remote = str(remote_sel.value) if remote_sel.value != Select.BLANK else ""
+            remote = str(remote_sel.value) if isinstance(remote_sel.value, str) else ""
             msg = f"Run backup for target '{target}'?"
             if remote:
                 msg += f"\nRemote: {remote}"

tui/screens/remote_edit.py

@@ -95,7 +95,7 @@ class RemoteEditScreen(Screen):
 
     def _update_field_visibility(self) -> None:
         type_sel = self.query_one("#re-type", Select)
-        rtype = str(type_sel.value) if type_sel.value is not Select.BLANK else "ssh"
+        rtype = str(type_sel.value) if isinstance(type_sel.value, str) else "ssh"
         for w in self.query(".ssh-field"):
             w.display = rtype == "ssh"
         for w in self.query(".s3-field"):
@@ -125,7 +125,7 @@ class RemoteEditScreen(Screen):
             name = self._edit_name
 
         type_sel = self.query_one("#re-type", Select)
-        rtype = str(type_sel.value) if type_sel.value is not Select.BLANK else "ssh"
+        rtype = str(type_sel.value) if isinstance(type_sel.value, str) else "ssh"
 
         remote = Remote(
             name=name,
@@ -133,7 +133,7 @@ class RemoteEditScreen(Screen):
             host=self.query_one("#re-host", Input).value.strip(),
             port=self.query_one("#re-port", Input).value.strip() or "22",
             user=self.query_one("#re-user", Input).value.strip() or "root",
-            auth_method=str(self.query_one("#re-auth", Select).value) if self.query_one("#re-auth", Select).value is not Select.BLANK else "key",
+            auth_method=str(self.query_one("#re-auth", Select).value) if isinstance(self.query_one("#re-auth", Select).value, str) else "key",
             key=self.query_one("#re-key", Input).value.strip(),
             password=self.query_one("#re-password", Input).value,
             base=self.query_one("#re-base", Input).value.strip() or "/backups",

tui/screens/restore.py

@@ -52,7 +52,7 @@ class RestoreScreen(Screen):
             remote_sel = self.query_one("#restore-remote", Select)
         except Exception:
             return
-        if target_sel.value is Select.BLANK or remote_sel.value is Select.BLANK:
+        if not isinstance(target_sel.value, str) or not isinstance(remote_sel.value, str):
             return
         target = str(target_sel.value)
         remote = str(remote_sel.value)
@@ -85,13 +85,13 @@ class RestoreScreen(Screen):
         target_sel = self.query_one("#restore-target", Select)
         remote_sel = self.query_one("#restore-remote", Select)
         snap_sel = self.query_one("#restore-snapshot", Select)
-        if target_sel.value is Select.BLANK:
+        if not isinstance(target_sel.value, str):
             self.notify("Select a target", severity="error")
             return
-        if remote_sel.value is Select.BLANK:
+        if not isinstance(remote_sel.value, str):
             self.notify("Select a remote", severity="error")
             return
-        if snap_sel.value is Select.BLANK:
+        if not isinstance(snap_sel.value, str):
             self.notify("Select a snapshot", severity="error")
             return
         target = str(target_sel.value)

tui/screens/retention.py

@@ -45,7 +45,7 @@ class RetentionScreen(Screen):
             self.app.pop_screen()
         elif event.button.id == "btn-cleanup":
             target_sel = self.query_one("#ret-target", Select)
-            if target_sel.value is Select.BLANK:
+            if not isinstance(target_sel.value, str):
                 self.notify("Select a target first", severity="error")
                 return
             target = str(target_sel.value)

tui/screens/schedule.py

@@ -108,7 +108,7 @@ class ScheduleScreen(Screen):
             self.notify(f"Schedule '{name}' already exists.", severity="error")
             return
         type_sel = self.query_one("#sched-type", Select)
-        stype = str(type_sel.value) if type_sel.value is not Select.BLANK else "daily"
+        stype = str(type_sel.value) if isinstance(type_sel.value, str) else "daily"
         sched = Schedule(
             name=name,
             schedule=stype,

tui/screens/settings.py

@@ -72,7 +72,7 @@ class SettingsScreen(Screen):
 
     def _get_select_val(self, sel_id: str, default: str) -> str:
         sel = self.query_one(sel_id, Select)
-        return str(sel.value) if sel.value is not Select.BLANK else default
+        return str(sel.value) if isinstance(sel.value, str) else default
 
     def _save(self) -> None:
         settings = AppSettings(

tui/screens/snapshots.py

@@ -47,7 +47,7 @@ class SnapshotsScreen(Screen):
     async def _load_snapshots(self) -> None:
         target_sel = self.query_one("#snap-target", Select)
         remote_sel = self.query_one("#snap-remote", Select)
-        if target_sel.value is Select.BLANK or remote_sel.value is Select.BLANK:
+        if not isinstance(target_sel.value, str) or not isinstance(remote_sel.value, str):
             self.notify("Select target and remote first", severity="error")
             return
         target = str(target_sel.value)