M8.12: Perspective Selection tool scales, copies, moves perpendicular and nudges in perspective

The Perspective Selection tool shows the selection's bounding box in perspective; its handles
scale in plane space (perspective.transform; Shift proportional, Alt from the centre). Alt-drag
moves copies that stay attached, pressing 5 while dragging moves along the plane's normal
(ToolKey::Digit, delivered by the canvas and MCP press_key), and the arrow keys nudge in
perspective (perspective.nudge). Transform Again repeats the last perspective move or scale in
plane space. Attachments (plane and depth) now live on the objects (Node.perspective), so copies,
duplicates and pastes keep them; grids from older files hand theirs over. Homography moves to
vectorcraft-geom. Hint-bar text for the tool.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

crates/engine/src/lib.rs

@@ -81,6 +81,9 @@ pub struct Interaction {
     /// Per-document state restored on cancel (current layer, isolation).
     pub active_layer: Option<NodeId>,
     pub isolation: Option<NodeId>,
+    /// The perspective transform the previews make (`perspective.transform` params): Transform
+    /// Again repeats it once the drag is committed.
+    pub perspective_again: Option<Value>,
 }
 
 /// Per-document editing state.
@@ -131,6 +134,9 @@ pub struct DocState {
     pub recovery: Option<cmd::recovery::RecoveryCopy>,
     /// View → Show Print Tiling, per document (view state: not saved, not undoable).
     pub print_tiling: bool,
+    /// Transform Again after a perspective move or scale (Perspective Selection tool): the
+    /// `perspective.transform` params it repeats. `None` once an ordinary transform follows.
+    pub last_perspective: Option<Value>,
 }
 
 static NEXT_DOC_UID: std::sync::atomic::AtomicU64 = std::sync::atomic::AtomicU64::new(1);
@@ -163,6 +169,7 @@ impl DocState {
             recovered: false,
             recovery: None,
             print_tiling: false,
+            last_perspective: None,
         }
     }
     /// Unsaved changes: the document differs from the saved one (selection changes don't count).
@@ -1052,6 +1059,7 @@ impl Session {
             preview: None,
             active_layer: st.active_layer,
             isolation: st.isolation,
+            perspective_again: None,
         });
         Ok(())
     }
@@ -1080,14 +1088,19 @@ impl Session {
         let st = self.doc_mut()?;
         let Some(mut it) = st.interaction.take() else { return Ok(()) };
         let Some(preview) = it.preview.take() else { return Ok(()) };
+        let perspective_again = it.perspective_again.take();
         st.keep_interaction(it);
         if preview.0 == "object.transform" {
             let m = cmd::matrix_param(&preview.1, "matrix");
             let copy = preview.1.get("copy").and_then(Value::as_bool).unwrap_or(false);
             if let Some(m) = m {
                 st.last_transform = Some((m, copy));
+                st.last_perspective = None;
             }
         }
+        if perspective_again.is_some() {
+            st.last_perspective = perspective_again;
+        }
         self.journal.push(preview);
         Ok(())
     }
@@ -1256,6 +1269,8 @@ mod tests_pdfpresets;
 #[cfg(test)]
 mod tests_pdfraster;
 #[cfg(test)]
+mod tests_persp_select;
+#[cfg(test)]
 mod tests_perspgrid;
 #[cfg(test)]
 mod tests_place;