refactor: colocate cmd tests with their modules

Move tests from the monolithic tests.rs into #[cfg(test)] mod tests
blocks in each command module. Shared test helpers live in
mod.rs::test_helpers.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Executed-By: fido

src/command/cmd/mod.rs

@@ -16,4 +16,106 @@ pub use self::core::{Cmd, CmdContext, CmdRegistry};
 pub use registry::default_registry;
 
 #[cfg(test)]
-mod tests;
+pub(super) mod test_helpers {
+    use std::collections::HashMap;
+
+    use crossterm::event::KeyCode;
+
+    use crate::model::Model;
+    use crate::ui::app::AppMode;
+    use crate::ui::effect::Effect;
+    use crate::view::GridLayout;
+
+    use super::core::CmdContext;
+    use super::registry::default_registry;
+
+    pub type CmdRegistry = super::core::CmdRegistry;
+
+    pub static EMPTY_BUFFERS: std::sync::LazyLock<HashMap<String, String>> =
+        std::sync::LazyLock::new(HashMap::new);
+    pub static EMPTY_EXPANDED: std::sync::LazyLock<std::collections::HashSet<String>> =
+        std::sync::LazyLock::new(std::collections::HashSet::new);
+
+    pub fn make_layout(model: &Model) -> GridLayout {
+        GridLayout::new(model, model.active_view())
+    }
+
+    pub fn make_ctx<'a>(
+        model: &'a Model,
+        layout: &'a GridLayout,
+        registry: &'a CmdRegistry,
+    ) -> CmdContext<'a> {
+        let view = model.active_view();
+        let (sr, sc) = view.selected;
+        CmdContext {
+            model,
+            layout,
+            registry,
+            mode: &AppMode::Normal,
+            selected: view.selected,
+            row_offset: view.row_offset,
+            col_offset: view.col_offset,
+            search_query: "",
+            yanked: &None,
+            dirty: false,
+            search_mode: false,
+            formula_panel_open: false,
+            category_panel_open: false,
+            view_panel_open: false,
+            formula_cursor: 0,
+            cat_panel_cursor: 0,
+            view_panel_cursor: 0,
+            tile_cat_idx: 0,
+            buffers: &EMPTY_BUFFERS,
+            view_back_stack: &[],
+            view_forward_stack: &[],
+            display_value: {
+                let key = layout.cell_key(sr, sc);
+                key.as_ref()
+                    .and_then(|k| model.get_cell(k).cloned())
+                    .map(|v| v.to_string())
+                    .unwrap_or_default()
+            },
+            visible_rows: 20,
+            visible_cols: 8,
+            expanded_cats: &EMPTY_EXPANDED,
+            key_code: KeyCode::Null,
+        }
+    }
+
+    pub fn two_cat_model() -> Model {
+        let mut m = Model::new("Test");
+        m.add_category("Type").unwrap();
+        m.add_category("Month").unwrap();
+        m.category_mut("Type").unwrap().add_item("Food");
+        m.category_mut("Type").unwrap().add_item("Clothing");
+        m.category_mut("Month").unwrap().add_item("Jan");
+        m.category_mut("Month").unwrap().add_item("Feb");
+        m
+    }
+
+    pub fn three_cat_model_with_page() -> Model {
+        let mut m = Model::new("Test");
+        m.add_category("Type").unwrap();
+        m.add_category("Month").unwrap();
+        m.add_category("Region").unwrap();
+        m.category_mut("Type").unwrap().add_item("Food");
+        m.category_mut("Type").unwrap().add_item("Clothing");
+        m.category_mut("Month").unwrap().add_item("Jan");
+        m.category_mut("Month").unwrap().add_item("Feb");
+        m.category_mut("Region").unwrap().add_item("North");
+        m.category_mut("Region").unwrap().add_item("South");
+        m.category_mut("Region").unwrap().add_item("East");
+        let view = m.active_view_mut();
+        view.set_axis("Region", crate::view::Axis::Page);
+        m
+    }
+
+    pub fn effects_debug(effects: &[Box<dyn Effect>]) -> String {
+        format!("{:?}", effects)
+    }
+
+    pub fn make_registry() -> CmdRegistry {
+        default_registry()
+    }
+}