Co-locate CadCommand impls with their ribbon toolbar modules

Each command implementation is now in the same file as its ribbon
tool definition. Groups moved to a dedicated groups/ toolbar folder.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

src/modules/home/modify/group.rs

@@ -1,12 +0,0 @@
-// Group tool — ribbon definition.
-
-use crate::modules::{IconKind, ModuleEvent, ToolDef};
-
-pub fn tool() -> ToolDef {
-    ToolDef {
-        id: "GROUP",
-        label: "Group",
-        icon: IconKind::Svg(include_bytes!("../../../../assets/icons/group.svg")),
-        event: ModuleEvent::Command("GROUP".to_string()),
-    }
-}

src/modules/home/modify/mod.rs

@@ -4,7 +4,6 @@ pub mod delete;
 pub mod explode;
 mod extend;
 pub mod fillet;
-pub mod group;
 pub mod mirror;
 pub mod offset;
 pub mod rotate;
@@ -12,4 +11,3 @@ pub mod scale;
 pub mod stretch;
 pub mod translate;
 pub mod trim;
-pub mod ungroup;

src/modules/home/modify/ungroup.rs

@@ -1,12 +0,0 @@
-// Ungroup tool — ribbon definition.
-
-use crate::modules::{IconKind, ModuleEvent, ToolDef};
-
-pub fn tool() -> ToolDef {
-    ToolDef {
-        id: "UNGROUP",
-        label: "Ungroup",
-        icon: IconKind::Svg(include_bytes!("../../../../assets/icons/ungroup.svg")),
-        event: ModuleEvent::Command("UNGROUP".to_string()),
-    }
-}