Guides: the ruler guide export test leaves out the PDF's dates

exports_and_fit_all_are_the_same_with_ruler_guides compared PDF exports
byte for byte, but each export carries the time it was written in
/ModDate and the XMP packet. Two exports in different seconds differed,
so the test failed now and then in CI. The test now drops the dated
lines from the PDF before comparing, as undated in the envelope tests
does. SVG, PNG and PSD are still compared whole.

crates/engine/tests/it/ruler_guide_nodes.rs

@@ -257,14 +257,25 @@ fn guides_made_while_editing_a_mask_a_pattern_or_a_symbol_stay() {
     assert!(!in_symbol, "the guide is not part of the symbol");
 }
 
+/// `bytes` without the lines that depend on when the file was written: the PDF dates, and the XMP
+/// packet (one line, with its dates and IDs) and trailer `/ID`.
+fn undated(bytes: &[u8]) -> Vec<u8> {
+    let stamps: [&[u8]; 5] = [b"CreationDate", b"ModDate", b"xmp:CreateDate", b"xmp:ModifyDate", b"/ID["];
+    let dated = |line: &&[u8]| stamps.iter().any(|s| line.windows(s.len()).any(|w| w == *s));
+    bytes.split(|b| *b == b'\n').filter(|l| !dated(l)).flat_map(|l| l.iter().copied().chain(*b"\n")).collect()
+}
+
 /// The bytes of each export format (PDF without the embedded native document, which keeps the
-/// guides), and the box Fit All in Window fits (the art and every artboard).
-fn exports(s: &mut Session) -> (Vec<(String, String)>, Option<vectorcraft_geom::Rect>) {
+/// guides, and without its dates), and the box Fit All in Window fits (the art and every artboard).
+fn exports(s: &mut Session) -> (Vec<(String, Vec<u8>)>, Option<vectorcraft_geom::Rect>) {
     let files = [json!({"format": "svg"}), json!({"format": "pdf", "preserveEditing": false}), json!({"format": "png"}), json!({"format": "psd"})]
         .iter()
         .map(|p| {
             let out = s.execute("document.export", p).unwrap();
-            (p["format"].as_str().unwrap().to_string(), out["dataBase64"].as_str().unwrap().to_string())
+            let bytes = vectorcraft_format::base64_decode(out["dataBase64"].as_str().unwrap()).unwrap();
+            let format = p["format"].as_str().unwrap().to_string();
+            let bytes = if format == "pdf" { undated(&bytes) } else { bytes };
+            (format, bytes)
         })
         .collect();
     let d = &s.doc().unwrap().doc;