feat(gui): advanced expander surfaces non-master PAM stacks in Policy tab

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

gui/src/policy_page.rs

@@ -141,6 +141,53 @@ impl PolicyPage {
         }
         pref_page.add(&group);
 
+        // Advanced expander — non-master stacks the daemon discovered. Toggling
+        // any of these triggers polkit at SetPolicy time; no special GUI plumbing.
+        let advanced_group = adw::PreferencesGroup::new();
+        let expander = adw::ExpanderRow::builder()
+            .title("Advanced")
+            .subtitle("Per-stack overrides for any PAM stack the daemon knows about.")
+            .build();
+
+        let mut others: Vec<&String> = current
+            .stacks
+            .keys()
+            .filter(|k| !MASTER_STACKS.contains(&k.as_str()))
+            .collect();
+        others.sort();
+        for stack_name in others {
+            let mode = current
+                .stacks
+                .get(stack_name)
+                .map(|s| s.mode)
+                .unwrap_or(Mode::Disabled);
+            let labels: Vec<&str> = MODE_LABELS.iter().map(|(l, _)| *l).collect();
+            let model = gtk::StringList::new(&labels);
+            let combo = adw::ComboRow::builder()
+                .title(stack_name.as_str())
+                .model(&model)
+                .selected(mode_to_combo_index(mode))
+                .build();
+            let me = self.clone();
+            let s = stack_name.clone();
+            combo.connect_selected_notify(move |c| {
+                let new_mode = combo_index_to_mode(c.selected());
+                me.working
+                    .borrow_mut()
+                    .stacks
+                    .entry(s.clone())
+                    .or_insert(StackPolicy {
+                        mode: Mode::Disabled,
+                        methods: vec![Method::Fido2],
+                    })
+                    .mode = new_mode;
+            });
+            expander.add_row(&combo);
+        }
+
+        advanced_group.add(&expander);
+        pref_page.add(&advanced_group);
+
         // Apply button row at the bottom.
         let apply_group = adw::PreferencesGroup::new();
         let apply = adw::ActionRow::builder()