engine: protected sheets gate filter reapply, outline, line sizes and floating pictures; pivot destination resolved before the structure check; user-limited edit ranges stay locked (#3296)

crates/engine/src/cmd/insert.rs

@@ -1100,6 +1100,10 @@ fn insert_picture(s: &mut Session, p: &Json) -> Result<Json> {
         .unwrap_or_else(|| if data.starts_with(&[0x89, b'P', b'N', b'G']) { "image/png".into() } else { "image/jpeg".into() });
     let (w, h) = crate::io::image_size(&data).unwrap_or((320, 240));
     let d = s.doc()?;
+    // Sheet protection locks drawing objects, as for a text box's text.
+    if d.wb.active().is_some_and(|sh| sh.is_protected()) {
+        return Err(EngineError::Other(PROTECTED.into()));
+    }
     let id = d.wb.next_object_id();
     let at = cell_param(s, p, "at")?.unwrap_or(d.selection.active);
     let scale = (640.0 / w.max(1) as f32).min(1.0);