Fix cancel_input bug, scope selection on datasets, is_marked perf

- cancel_input: mode was set to Normal before checking if Search,
  so search query was never cleared on Esc
- select_group/unselect_group/invert: use dataset full_name as scope
  when cursor is on a dataset (previously used parent_path which
  matched nothing)
- is_marked: avoid unnecessary String allocation per comparison

src/app.rs

@@ -351,7 +351,7 @@ impl App {
     }
 
     pub fn is_marked(&self, name: &str) -> bool {
-        self.marked.contains(&name.to_string())
+        self.marked.iter().any(|x| x == name)
     }
 
     pub fn delete_marked(&mut self) -> Result<()> {
@@ -438,8 +438,9 @@ impl App {
     }
 
     pub fn cancel_input(&mut self) {
+        let was_search = self.input_mode == InputMode::Search;
         self.input_mode = InputMode::Normal;
-        if self.input_mode == InputMode::Search {
+        if was_search {
             self.search_query.clear();
             self.search_matches.clear();
         }
@@ -585,13 +586,22 @@ impl App {
         }
     }
 
-    // Select/Unselect Group (like MC) - works in current scope
-    pub fn select_group(&mut self) {
-        let current_parent = if let Some(real_idx) = self.nth_visible(self.selected) {
-            self.tree_items.get(real_idx).map(|ti| ti.parent_path.clone())
+    // Get the scope parent: if cursor is on a dataset, use its full_name;
+    // if on a snapshot, use its parent_path (the owning dataset)
+    fn current_scope_parent(&self) -> Option<String> {
+        if let Some(real_idx) = self.nth_visible(self.selected) {
+            self.tree_items.get(real_idx).map(|ti| match &ti.item {
+                ListItem::Dataset(d) => d.full_name.clone(),
+                ListItem::Snapshot(_) => ti.parent_path.clone(),
+            })
         } else {
             None
-        };
+        }
+    }
+
+    // Select/Unselect Group (like MC) - works in current scope
+    pub fn select_group(&mut self) {
+        let current_parent = self.current_scope_parent();
 
         let mut count = 0;
         for ti in &self.tree_items {
@@ -614,11 +624,7 @@ impl App {
     }
 
     pub fn unselect_group(&mut self) {
-        let current_parent = if let Some(real_idx) = self.nth_visible(self.selected) {
-            self.tree_items.get(real_idx).map(|ti| ti.parent_path.clone())
-        } else {
-            None
-        };
+        let current_parent = self.current_scope_parent();
 
         let visible_names: Vec<String> = self.tree_items
             .iter()
@@ -641,12 +647,7 @@ impl App {
     }
 
     pub fn invert_selection(&mut self) {
-        // Get current scope (parent dataset of selected item)
-        let current_parent = if let Some(real_idx) = self.nth_visible(self.selected) {
-            self.tree_items.get(real_idx).map(|ti| ti.parent_path.clone())
-        } else {
-            None
-        };
+        let current_parent = self.current_scope_parent();
 
         let mut count = 0;
         for ti in &self.tree_items {