Part of #758: .ai import doesn't weigh text objects when the layers can't be used

Before deciding to use the layers of an Illustrator file, the import
drew them again for each text object made from the file's text
document, to see whether the page draws it. When the layers differ from
the page by more than the check allows even with every such object
gone (taking one out only changes what is drawn in its box), the
layers aren't used whatever is taken out: that weighing is now
skipped.

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

crates/eps/src/import/native.rs

@@ -936,6 +936,14 @@ fn prune_unseen(frame: &Frame<'_>, view: &mut PageView, doc: &mut Document) -> u
         return 0;
     }
     let mut with = view.difference(doc, rect).any;
+    // Taking a text object out changes only what is drawn in its box. When the art would still
+    // differ from the page by more than `compare` allows with every candidate gone, the layers
+    // aren't used whatever is pruned: don't draw them again for each one (#758).
+    let margin = OUTLINE_REACH + 1.0;
+    let boxes: f64 = found.iter().filter_map(|(_, b)| *b).map(|b| b.inflate(margin, margin).intersect(rect).area().max(0.0)).sum();
+    if with - boxes / rect.area().max(1e-9) > MAX_DIFFERENCE {
+        return 0;
+    }
     let mut removed = 0;
     for (id, bounds) in found {
         if bounds.is_none_or(|b| b.intersect(rect).is_zero_area()) {