refactor(modules): rename home module to draw, restore first-tab order

The Home tab was already titled "Draw"; rename the module to match:
folder modules/home → modules/draw, HomeModule → DrawModule, id "home"
→ "draw". The inner draw/ command folder is kept (modules::draw::draw).

Update build.rs PRIORITY ("home" → "draw") so the tab returns to the
front of the ribbon; registry.rs regenerates accordingly.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

src/modules/draw/groups/group.rs

@@ -0,0 +1,74 @@
+// Group tool — ribbon definition + CadCommand implementation.
+
+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()),
+    }
+}
+
+// ── CadCommand implementation ─────────────────────────────────────────────
+
+use acadrust::Handle;
+use glam::Vec3;
+
+use crate::command::{CadCommand, CmdResult};
+use crate::scene::model::wire_model::WireModel;
+
+pub struct GroupCommand {
+    handles: Vec<Handle>,
+    /// Auto-generated fallback name shown in the prompt.
+    auto_name: String,
+}
+
+impl GroupCommand {
+    pub fn new(handles: Vec<Handle>, auto_name: String) -> Self {
+        Self { handles, auto_name }
+    }
+}
+
+impl CadCommand for GroupCommand {
+    fn name(&self) -> &'static str {
+        "GROUP"
+    }
+
+    fn prompt(&self) -> String {
+        format!("GROUP  Enter group name [{}]:", self.auto_name)
+    }
+
+    fn wants_text_input(&self) -> bool {
+        true
+    }
+
+    fn on_text_input(&mut self, text: &str) -> Option<CmdResult> {
+        let name = if text.trim().is_empty() {
+            std::mem::take(&mut self.auto_name)
+        } else {
+            text.trim().to_string()
+        };
+        Some(CmdResult::CreateGroup {
+            handles: std::mem::take(&mut self.handles),
+            name,
+        })
+    }
+
+    fn on_enter(&mut self) -> CmdResult {
+        // Enter with no typed name uses the auto-generated name.
+        CmdResult::CreateGroup {
+            handles: std::mem::take(&mut self.handles),
+            name: std::mem::take(&mut self.auto_name),
+        }
+    }
+
+    fn on_point(&mut self, _pt: Vec3) -> CmdResult {
+        CmdResult::NeedPoint
+    }
+
+    fn on_hover_entity(&mut self, _handle: Handle, _pt: Vec3) -> Vec<WireModel> {
+        vec![]
+    }
+}

src/modules/draw/groups/mod.rs

@@ -0,0 +1,2 @@
+pub mod group;
+pub mod ungroup;

src/modules/draw/groups/ungroup.rs

@@ -0,0 +1,65 @@
+// Ungroup tool — ribbon definition + CadCommand implementation.
+
+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()),
+    }
+}
+
+// ── CadCommand implementation ─────────────────────────────────────────────
+
+use acadrust::Handle;
+use glam::Vec3;
+
+use crate::command::{CadCommand, CmdResult};
+use crate::scene::model::wire_model::WireModel;
+
+pub struct UngroupCommand;
+
+impl UngroupCommand {
+    pub fn new() -> Self {
+        Self
+    }
+}
+
+impl CadCommand for UngroupCommand {
+    fn name(&self) -> &'static str {
+        "UNGROUP"
+    }
+
+    fn prompt(&self) -> String {
+        "UNGROUP  Select grouped objects:".into()
+    }
+
+    fn is_selection_gathering(&self) -> bool {
+        true
+    }
+
+    fn on_selection_complete(&mut self, handles: Vec<Handle>) -> CmdResult {
+        if handles.is_empty() {
+            return CmdResult::NeedPoint;
+        }
+        CmdResult::DeleteGroups { handles }
+    }
+
+    fn on_point(&mut self, _pt: Vec3) -> CmdResult {
+        CmdResult::NeedPoint
+    }
+
+    fn on_enter(&mut self) -> CmdResult {
+        CmdResult::Cancel
+    }
+
+    fn on_hover_entity(&mut self, _handle: Handle, _pt: Vec3) -> Vec<WireModel> {
+        vec![]
+    }
+}
+
+
+// ── Autocomplete registry ─────────────────────────────────
+inventory::submit!(crate::command::CommandRegistration { names: &["UG", "UNGROUP"] });  // UngroupCommand