[ZZ1] insert.dateTime in the Handout/Notes Master view fills the master's date placeholder

PowerPoint: Header and Footer > Notes and Handouts > Date and time puts a date field in the
date placeholder of the notes and handout masters, and every handout and notes page shows it.
Before, with no text caret the command wrote the current slide's date placeholder (design
.headerFooter) even in those views, so the handout PDF showed nothing. Now it writes the selected
date placeholder, else the master's own, as a field (update) or plain text, answers where:
master, and refuses (changing nothing) when the master has no date placeholder.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

crates/engine/src/cmd/insert.rs

@@ -98,7 +98,7 @@ pub fn specs() -> Vec<CommandSpec> {
             "Date & Time",
             ["Insert", "Text"],
             None,
-            "{format?: datetime1..datetime13, update?: bool, language?: en-US|en-GB|fr-FR|ja-JP|sv-SE} — no keys opens the dialog",
+            "{format?: datetime1..datetime13, update?: bool, language?: en-US|en-GB|fr-FR|ja-JP|sv-SE} — no keys opens the dialog; in the Handout or Notes Master view it fills the selected date placeholder (else the master's own) and answers where: \"master\"",
             has_slide,
             date_time
         ),
@@ -473,6 +473,70 @@ mod tests {
         }
     }
 
+    /// ZZ1: in the handout and notes master views the date goes into the master's date placeholder
+    /// (not the current slide), so the exported handout and notes pages show it.
+    #[test]
+    fn on_a_page_master_the_date_fills_its_date_placeholder() {
+        for view in ["view.handoutMaster", "view.notesMaster"] {
+            let mut s = session();
+            s.execute(view, &json!({})).unwrap();
+            let (id, master) = {
+                let st = s.doc().unwrap();
+                let m = crate::page_master(&st.doc, st.selection.target).unwrap().clone();
+                (m.shapes.iter().find(|x| x.ph_type() == Some(deckcraft_model::PhType::Date)).unwrap().id.0, m)
+            };
+            assert!(master.shapes.iter().find(|x| x.id.0 == id).and_then(|x| x.text.as_ref()).is_none_or(|t| t.text().is_empty()));
+            s.execute("edit.select", &json!({"ids": [id]})).unwrap();
+            let v = s.execute("insert.dateTime", &json!({"format": "datetime10", "update": true})).unwrap();
+            assert_eq!(v["where"], "master", "{view}: {v}");
+            assert!(date_run(&s).is_none(), "the slide keeps no date");
+            let st = s.doc().unwrap();
+            let m = crate::page_master(&st.doc, st.selection.target).unwrap();
+            let run = m
+                .shapes
+                .iter()
+                .find(|x| x.id.0 == id)
+                .and_then(|x| x.text.as_ref())
+                .and_then(|t| t.paragraphs.first())
+                .and_then(|p| p.runs.first())
+                .cloned()
+                .unwrap();
+            assert!(matches!(run.kind, RunKind::Field { ref field } if field == "datetime10"), "{view}: {run:?}");
+            let placed = deckcraft_render::place_master_texts(&st.doc, m, 1);
+            assert!(placed.iter().any(|p| p.body.text() == run.text && run.text.contains(':')), "{view}: the page shows the date");
+            s.execute("edit.undo", &json!({})).unwrap();
+            let st = s.doc().unwrap();
+            let m = crate::page_master(&st.doc, st.selection.target).unwrap();
+            assert!(m.shapes.iter().find(|x| x.id.0 == id).and_then(|x| x.text.as_ref()).is_none_or(|t| t.text().is_empty()), "one undo");
+            // A fixed date in a placeholder whose run is en-GB reads day first, and the answer
+            // reports the text that was written, not the en-US sample.
+            s.execute("insert.dateTime", &json!({"format": "datetime1", "update": false, "language": "en-GB"})).unwrap();
+            let v = s.execute("insert.dateTime", &json!({"format": "datetime1", "update": false})).unwrap();
+            let st = s.doc().unwrap();
+            let m = crate::page_master(&st.doc, st.selection.target).unwrap();
+            let run = m
+                .shapes
+                .iter()
+                .find(|x| x.id.0 == id)
+                .and_then(|x| x.text.as_ref())
+                .and_then(|t| t.paragraphs.first())
+                .and_then(|p| p.runs.first())
+                .cloned()
+                .unwrap();
+            assert_eq!(run.props.lang.as_deref(), Some("en-GB"), "{view}: {run:?}");
+            assert_eq!(v["text"].as_str(), Some(run.text.as_str()), "{view}: the answer reports the written text: {v}");
+            let now = deckcraft_text::datetime::DateTime::now_local().unwrap();
+            let gb = deckcraft_text::datetime::field_text("datetime1", Some("en-GB"), now);
+            assert_eq!(Some(run.text.as_str()), gb.as_deref(), "{view}: the date in en-GB order (dd/mm/yyyy)");
+            // No date placeholder: refused, nothing changed.
+            let key = if view == "view.handoutMaster" { "handout.placeholders" } else { "notes.placeholders" };
+            s.execute(key, &json!({"date": false})).unwrap();
+            let rev = s.doc().unwrap().revision;
+            assert!(s.execute("insert.dateTime", &json!({"format": "datetime1"})).is_err());
+            assert_eq!(s.doc().unwrap().revision, rev);
+        }
+    }
+
     #[test]
     fn without_a_caret_the_date_lands_on_this_slide_only() {
         let mut s = session();