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/mode.rs

@@ -4,6 +4,125 @@ use crate::ui::effect::{self, Effect};
 use super::core::{Cmd, CmdContext};
 use super::grid::DrillIntoCell;
 
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use crate::command::cmd::test_helpers::*;
+    use crate::model::Model;
+
+    #[test]
+    fn enter_edit_mode_produces_editing_mode() {
+        let m = two_cat_model();
+        let layout = make_layout(&m);
+        let reg = make_registry();
+        let ctx = make_ctx(&m, &layout, &reg);
+        let cmd = EnterEditMode {
+            initial_value: String::new(),
+        };
+        let effects = cmd.execute(&ctx);
+        assert_eq!(effects.len(), 2);
+        let dbg = format!("{:?}", effects[1]);
+        assert!(dbg.contains("Editing"), "Expected Editing mode, got: {dbg}");
+    }
+
+    #[test]
+    fn enter_tile_select_with_categories() {
+        let m = two_cat_model();
+        let layout = make_layout(&m);
+        let reg = make_registry();
+        let ctx = make_ctx(&m, &layout, &reg);
+        let cmd = EnterTileSelect;
+        let effects = cmd.execute(&ctx);
+        assert_eq!(effects.len(), 2);
+        let dbg = format!("{:?}", effects[1]);
+        assert!(
+            dbg.contains("TileSelect"),
+            "Expected TileSelect mode, got: {dbg}"
+        );
+    }
+
+    #[test]
+    fn enter_tile_select_no_categories() {
+        let m = Model::new("Empty");
+        let layout = make_layout(&m);
+        let reg = make_registry();
+        let ctx = make_ctx(&m, &layout, &reg);
+        let cmd = EnterTileSelect;
+        let effects = cmd.execute(&ctx);
+        assert_eq!(effects.len(), 2);
+    }
+
+    #[test]
+    fn enter_export_prompt_sets_mode() {
+        let m = two_cat_model();
+        let layout = make_layout(&m);
+        let reg = make_registry();
+        let ctx = make_ctx(&m, &layout, &reg);
+        let effects = EnterExportPrompt.execute(&ctx);
+        let dbg = effects_debug(&effects);
+        assert!(
+            dbg.contains("ExportPrompt"),
+            "Expected ExportPrompt mode, got: {dbg}"
+        );
+    }
+
+    #[test]
+    fn force_quit_always_produces_quit_mode() {
+        let m = two_cat_model();
+        let layout = make_layout(&m);
+        let reg = make_registry();
+        let mut ctx = make_ctx(&m, &layout, &reg);
+        ctx.dirty = true;
+        let effects = ForceQuit.execute(&ctx);
+        assert_eq!(effects.len(), 1);
+        let dbg = effects_debug(&effects);
+        assert!(dbg.contains("Quit"), "Expected Quit mode, got: {dbg}");
+    }
+
+    #[test]
+    fn save_and_quit_produces_save_then_quit() {
+        let m = two_cat_model();
+        let layout = make_layout(&m);
+        let reg = make_registry();
+        let ctx = make_ctx(&m, &layout, &reg);
+        let effects = SaveAndQuit.execute(&ctx);
+        assert_eq!(effects.len(), 2);
+        let dbg = effects_debug(&effects);
+        assert!(dbg.contains("Save"), "Expected Save, got: {dbg}");
+        assert!(dbg.contains("Quit"), "Expected Quit, got: {dbg}");
+    }
+
+    #[test]
+    fn edit_or_drill_without_aggregation_enters_edit() {
+        let m = two_cat_model();
+        let layout = make_layout(&m);
+        let reg = make_registry();
+        let ctx = make_ctx(&m, &layout, &reg);
+        let effects = EditOrDrill.execute(&ctx);
+        let dbg = effects_debug(&effects);
+        assert!(dbg.contains("Editing"), "Expected Editing mode, got: {dbg}");
+    }
+
+    #[test]
+    fn enter_search_mode_sets_flag_and_clears_query() {
+        let m = two_cat_model();
+        let layout = make_layout(&m);
+        let reg = make_registry();
+        let ctx = make_ctx(&m, &layout, &reg);
+        let effects = EnterSearchMode.execute(&ctx);
+        assert_eq!(effects.len(), 2);
+        let dbg = effects_debug(&effects);
+        assert!(
+            dbg.contains("SetSearchMode(true)"),
+            "Expected search mode on, got: {dbg}"
+        );
+        assert!(
+            dbg.contains("SetSearchQuery"),
+            "Expected query reset, got: {dbg}"
+        );
+    }
+}
+
 // ── Mode change commands ─────────────────────────────────────────────────────
 
 #[derive(Debug)]