revert: restore thumbnail capture for native saves (#956)

src/app/mod.rs

@@ -671,6 +671,8 @@ pub(super) struct OpenCADStudio {
     main_window: Option<window::Id>,
     /// Hides drawing UI overlays for one thumbnail capture frame.
     thumbnail_capture_clean: bool,
+    #[cfg(not(target_arch = "wasm32"))]
+    pending_native_thumbnail_save: Option<PendingNativeThumbnailSave>,
     #[cfg(target_arch = "wasm32")]
     pending_web_thumbnail_save: Option<PendingWebThumbnailSave>,
     // ── Floating panel windows ────────────────────────────────────────────
@@ -1227,6 +1229,18 @@ pub(super) enum SaveContinuation {
     Quit,
 }
 
+#[derive(Debug, Clone)]
+#[cfg(not(target_arch = "wasm32"))]
+pub(super) struct PendingNativeThumbnailSave {
+    tab_id: u64,
+    path: PathBuf,
+    version: acadrust::DxfVersion,
+    purpose: SavePurpose,
+    continuation: SaveContinuation,
+    set_current_path: bool,
+    check_external_change: bool,
+}
+
 #[derive(Debug, Clone)]
 #[cfg(target_arch = "wasm32")]
 pub(super) struct PendingWebThumbnailSave {
@@ -2049,6 +2063,8 @@ pub enum Message {
     AutoSave,
     /// A clean viewport frame is ready for thumbnail capture.
     ThumbnailCaptureFrame,
+    /// Restore drawing UI after the compositor screenshot is captured.
+    ThumbnailCaptureFinished,
     /// Native background save/autosave completed.
     #[cfg(not(target_arch = "wasm32"))]
     SaveFinished(SaveOutcome),
@@ -3373,6 +3389,8 @@ impl OpenCADStudio {
             last_point: None,
             main_window: None,
             thumbnail_capture_clean: false,
+            #[cfg(not(target_arch = "wasm32"))]
+            pending_native_thumbnail_save: None,
             #[cfg(target_arch = "wasm32")]
             pending_web_thumbnail_save: None,
             color_pick_target: None,