C14.14: export HTML, HTML and folder, PDF (MuPDF story in the PDF worker) and plain text; print; rich copy

Co-Authored-By: Claude Opus 5.5 (1M context) <noreply@anthropic.com>

crates/ely-ui/src/i18n/mark.rs

@@ -56,7 +56,11 @@ pub(super) const EN: &[(&str, &str)] = &[
     ("mark.export.done", "Exported {name}"),
     ("mark.export.missing", "Exported without these images: {list}."),
     ("mark.export.diagrams", "Diagrams that did not draw stay as code, at lines {list}."),
-    ("mark.export.formula", "The formula at line {line} did not render: {error}."),
+    ("mark.export.formulas", "Formulas that did not render stay as code: {list}."),
+    ("mark.export.formula", "line {line}, {error}"),
+    ("mark.export.folder_taken", "{name} is already there; the pictures need that folder."),
+    ("mark.copy.rich", "Copy as Rich Text"),
+    ("mark.copy.failed", "Copying failed: {error}"),
     ("mark.export.failed", "The export failed: {error}"),
     ("mark.look.focus", "Focus Mode"),
     ("mark.look.typewriter", "Typewriter Scrolling"),
@@ -149,7 +153,11 @@ pub(super) const ZH_CN: &[(&str, &str)] = &[
     ("mark.export.done", "已导出 {name}"),
     ("mark.export.missing", "已导出，缺这些图片：{list}。"),
     ("mark.export.diagrams", "没能画出的图表保留为代码，在第 {list} 行。"),
-    ("mark.export.formula", "第 {line} 行的公式没能排出：{error}。"),
+    ("mark.export.formulas", "没能排出的公式保留为代码：{list}。"),
+    ("mark.export.formula", "第 {line} 行，{error}"),
+    ("mark.export.folder_taken", "{name} 已存在；图片要放进这个文件夹。"),
+    ("mark.copy.rich", "复制为富文本"),
+    ("mark.copy.failed", "复制失败：{error}"),
     ("mark.export.failed", "导出失败：{error}"),
     ("mark.look.focus", "专注模式"),
     ("mark.look.typewriter", "打字机滚动"),