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/command/cmd/core.rs

@@ -34,8 +34,8 @@ pub struct CmdContext<'a> {
     /// Named text buffers
     pub buffers: &'a HashMap<String, String>,
     /// View navigation stacks (for drill back/forward)
-    pub view_back_stack: &'a [String],
-    pub view_forward_stack: &'a [String],
+    pub view_back_stack: &'a [crate::ui::app::ViewFrame],
+    pub view_forward_stack: &'a [crate::ui::app::ViewFrame],
     /// Whether the app currently has an active drill snapshot.
     pub has_drill_state: bool,
     /// Display value at the cursor — works uniformly for pivot and records mode.