feat: DATAEXTRACTION — export entity data to CSV

- DATAEXTRACTION / EATTEXT / ATTEXT commands trigger an async save dialog
- Extracts all model-space entities with: Type, Handle, Layer, Color,
  Linetype, and a geometry summary per entity type (coords, radius, etc.)
- DataExtractionSave / DataExtractionSaveResult message pair drives
  the rfd save-file dialog asynchronously
- CSV fields are properly escaped (commas, quotes, newlines)
- ROADMAP.md: 12 DATAEXTRACTION marked ✅

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

src/app/commands.rs

@@ -1612,6 +1612,11 @@ impl H7CAD {
                 self.command_line.push_output(&format!("COUNT: {total} entity(ies) total."));
             }
 
+            "DATAEXTRACTION" | "EATTEXT" | "ATTEXT" => {
+                let csv = build_data_extraction_csv(&self.tabs[i].scene.document);
+                return Task::done(Message::DataExtractionSave(csv));
+            }
+
             // ── Find / Replace ────────────────────────────────────────────────
             // FIND <search>              — list all Text/MText/Dimension containing <search>
             // FIND <search> REPLACE <rep> — replace first occurrence (case-insensitive)
@@ -3613,3 +3618,71 @@ fn replace_entity_text(entity: &mut acadrust::EntityType, search: &str, rep: &st
     }
 }
 
+
+// ── DATAEXTRACTION ─────────────────────────────────────────────────────────
+
+/// Build a CSV string with one row per entity in model space.
+/// Columns: Type, Handle, Layer, Color, Linetype, ExtraInfo
+fn build_data_extraction_csv(doc: &acadrust::CadDocument) -> String {
+    use acadrust::EntityType;
+
+    let mut out = String::from("Type,Handle,Layer,Color,Linetype,ExtraInfo\n");
+
+    let ms_handle = doc.header.model_space_block_handle;
+    for e in doc.entities() {
+        // Skip Block/EndBlock sentinels and paper-space entities.
+        if matches!(e, EntityType::Block(_) | EntityType::BlockEnd(_)) {
+            continue;
+        }
+        if !ms_handle.is_null() && e.common().owner_handle != ms_handle {
+            continue;
+        }
+        let type_name = entity_type_name(e);
+        let handle = format!("{:X}", e.common().handle.value());
+        let layer = csv_escape(&e.common().layer);
+        let color = format!("{}", e.common().color);
+        let lt = csv_escape(&e.common().linetype);
+        let extra = csv_escape(&entity_extra_info(e));
+        out.push_str(&format!("{type_name},{handle},{layer},{color},{lt},{extra}\n"));
+    }
+    out
+}
+
+/// Return a short geometry summary for CSV ExtraInfo column.
+fn entity_extra_info(entity: &acadrust::EntityType) -> String {
+    use acadrust::EntityType;
+    match entity {
+        EntityType::Line(e) => format!(
+            "({:.3},{:.3})-({:.3},{:.3})",
+            e.start.x, e.start.y, e.end.x, e.end.y
+        ),
+        EntityType::Circle(e) => format!(
+            "C({:.3},{:.3}) R={:.3}",
+            e.center.x, e.center.y, e.radius
+        ),
+        EntityType::Arc(e) => format!(
+            "C({:.3},{:.3}) R={:.3} {:.1}°-{:.1}°",
+            e.center.x, e.center.y, e.radius, e.start_angle, e.end_angle
+        ),
+        EntityType::Text(e) => e.value.clone(),
+        EntityType::MText(e) => e.value.chars().take(60).collect(),
+        EntityType::Insert(e) => format!("BLK={} @({:.3},{:.3})", e.block_name, e.insert_point.x, e.insert_point.y),
+        EntityType::LwPolyline(e) => format!("{} vertices", e.vertices.len()),
+        EntityType::Polyline(e) => format!("{} vertices", e.vertices.len()),
+        EntityType::Polyline2D(e) => format!("{} vertices", e.vertices.len()),
+        EntityType::Polyline3D(e) => format!("{} vertices", e.vertices.len()),
+        EntityType::Hatch(e) => format!("PAT={}", e.pattern.name),
+        EntityType::Dimension(e) => format!("{:.3}", e.base().actual_measurement),
+        EntityType::Spline(e) => format!("{} ctrl pts", e.control_points.len()),
+        _ => String::new(),
+    }
+}
+
+/// Escape a string for a CSV field (wrap in quotes if it contains comma/quote/newline).
+fn csv_escape(s: &str) -> String {
+    if s.contains(',') || s.contains('"') || s.contains('\n') {
+        format!("\"{}\"", s.replace('"', "\"\""))
+    } else {
+        s.to_string()
+    }
+}