Fields: a date-time picture's quoted text is shown as it is

Word's date-time pictures (`DATE \@ "…"`) put literal text in single
quotes, two quotes in a row standing for one: `H' o''clock'` shows
"8 o'clock". The formatter read the quotes as text and the letters
inside as instructions (an `a` became AM or PM). Quoted text is now
shown as it is; an unclosed quote runs to the end.

Regression test: `date_pictures_keep_quoted_text`.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01GBVQLyDnrG8Tn1yDQcUabC

crates/engine/src/cmd/insert/items.rs

@@ -83,6 +83,22 @@ pub fn format_date_parts(fmt: &str, y: i64, m: usize, d: u32, (hh, mm, ss): (u32
     let mut i = 0;
     while i < chars.len() {
         let c = chars.get(i).copied().unwrap_or(' ');
+        // Text in single quotes is shown as it is; two quotes in a row are one.
+        if c == '\'' {
+            i += 1;
+            while let Some(&q) = chars.get(i) {
+                i += 1;
+                if q != '\'' {
+                    out.push(q);
+                } else if chars.get(i) == Some(&'\'') {
+                    out.push('\'');
+                    i += 1;
+                } else {
+                    break;
+                }
+            }
+            continue;
+        }
         // `am/pm` (any case) is one token: AM or PM.
         if chars.get(i..i + 5).is_some_and(|w| w.iter().collect::<String>().eq_ignore_ascii_case("am/pm")) {
             out.push_str(if hh < 12 { "AM" } else { "PM" });

crates/engine/src/cmd/insert/tests.rs

@@ -334,6 +334,15 @@ fn symbol_takes_its_own_font() {
     assert!(s.run("insert.symbol", &json!({"char": ""})).is_err());
 }
 
+#[test]
+fn date_pictures_keep_quoted_text() {
+    // Text in single quotes is shown as it is (Word's date-time picture); two quotes are one.
+    assert_eq!(format_date_parts("H' o''clock'", 2026, 10, 21, (8, 0, 0), 0), "8 o'clock");
+    assert_eq!(format_date_parts("'Day' d 'at' h", 2026, 10, 21, (17, 0, 0), 0), "Day 21 at 5");
+    // An unclosed quote runs to the end.
+    assert_eq!(format_date_parts("yyyy 'and so", 2026, 10, 21, (0, 0, 0), 0), "2026 and so");
+}
+
 #[test]
 fn date_pictures() {
     // Word accepts either case for the day and year instructions.