feat(command): add smart edit-or-drill for aggregated cells

Introduce EditOrDrill command that intelligently handles
editing based on cell type. When cursor is on an aggregated
pivot cell (categories on Axis::None, no records mode), it
drills into the cell. Otherwise, it enters edit mode with
the current displayed value.

The 'i' and 'a' keys now trigger edit-or-drill instead of
enter-edit-mode. Aggregated cells are styled in italic to
signal that drilling is required for editing.

Co-Authored-By: fiddlerwoaroof/git-smart-commit (unsloth/Qwen3.5-35B-A3B-GGUF:Q5_K_M)

src/command/cmd.rs

@@ -633,6 +633,40 @@ impl Cmd for EnterEditMode {
     }
 }
 
+/// Smart dispatch for i/a: if the cursor is on an aggregated pivot cell
+/// (categories on `Axis::None`, no records mode), drill into it instead of
+/// editing. Otherwise enter edit mode with the current displayed value.
+#[derive(Debug)]
+pub struct EditOrDrill;
+impl Cmd for EditOrDrill {
+    fn name(&self) -> &'static str {
+        "edit-or-drill"
+    }
+    fn execute(&self, ctx: &CmdContext) -> Vec<Box<dyn Effect>> {
+        let is_aggregated = ctx.records_col.is_none() && !ctx.none_cats.is_empty();
+        if is_aggregated {
+            let Some(key) = ctx.cell_key.clone() else {
+                return vec![effect::set_status(
+                    "cannot drill — no cell at cursor",
+                )];
+            };
+            return DrillIntoCell { key }.execute(ctx);
+        }
+        // Edit path: prefer records display value (includes pending edits),
+        // else the underlying cell's stored value.
+        let initial_value = if let Some(v) = &ctx.records_value {
+            v.clone()
+        } else {
+            ctx.cell_key
+                .as_ref()
+                .and_then(|k| ctx.model.get_cell(k).cloned())
+                .map(|v| v.to_string())
+                .unwrap_or_default()
+        };
+        EnterEditMode { initial_value }.execute(ctx)
+    }
+}
+
 /// Typewriter-style advance: move down, wrap to top of next column at bottom.
 #[derive(Debug)]
 pub struct EnterAdvance {
@@ -2341,6 +2375,7 @@ pub fn default_registry() -> CmdRegistry {
             }))
         },
     );
+    r.register_nullary(|| Box::new(EditOrDrill));
     r.register_nullary(|| Box::new(EnterExportPrompt));
     r.register_nullary(|| Box::new(EnterFormulaEdit));
     r.register_nullary(|| Box::new(EnterTileSelect));