refactor(navigation): include AppMode in view navigation stack

Introduce `ViewFrame` to store both the view name and the `AppMode` when
pushing to the navigation stack. Update `view_back_stack` and
`view_forward_stack` to use `ViewFrame` instead of `String` . Update
`CmdContext` and `Effect` implementations (SwitchView, ViewBack,
ViewForward) to handle the new `ViewFrame` structure. Add `is_editing()`
helper to `AppMode` .

Co-Authored-By: fiddlerwoaroof/git-smart-commit (gemma-4-26B-A4B-it-UD-Q5_K_XL.gguf)

src/ui/app.rs

@@ -20,6 +20,13 @@ use crate::ui::grid::{
 };
 use crate::view::GridLayout;
 
+/// A saved view+mode pair for the navigation stack.
+#[derive(Debug, Clone, PartialEq)]
+pub struct ViewFrame {
+    pub view_name: String,
+    pub mode: AppMode,
+}
+
 /// Drill-down state: frozen record snapshot + pending edits that have not
 /// yet been applied to the model.
 #[derive(Debug, Clone, Default)]
@@ -88,6 +95,11 @@ impl AppMode {
         }
     }
 
+    /// True for any cell-editing mode (normal or records).
+    pub fn is_editing(&self) -> bool {
+        matches!(self, Self::Editing { .. } | Self::RecordsEditing { .. })
+    }
+
     pub fn editing() -> Self {
         Self::Editing {
             minibuf: MinibufferConfig {
@@ -173,9 +185,9 @@ pub struct App {
     pub tile_cat_idx: usize,
     /// View navigation history: views visited before the current one.
     /// Pushed on SwitchView, popped by `<` (back).
-    pub view_back_stack: Vec<String>,
+    pub view_back_stack: Vec<ViewFrame>,
     /// Views that were "back-ed" from, available for forward navigation (`>`).
-    pub view_forward_stack: Vec<String>,
+    pub view_forward_stack: Vec<ViewFrame>,
     /// Frozen records list for the drill view. When present, this is the
     /// snapshot that records-mode layouts iterate — records don't disappear
     /// when filters would change. Pending edits are stored alongside and