Start a new paragraph when an HTML block tag opens in paste

Found while testing crates/engine/src/cmd/richclip.rs:121-170 (html_to_body, opening-tag handling; is_block at :190)

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

crates/engine/src/cmd/richclip.rs

@@ -123,6 +123,9 @@ pub fn html_to_body(html: &str) -> Option<TextBody> {
                 }
                 continue;
             }
+            if is_block(&name) {
+                new_para(&mut paragraphs);
+            }
             if is_break(&name) {
                 new_para(&mut paragraphs);
                 continue;
@@ -368,6 +371,15 @@ fn fold(s: &str) -> String {
 mod tests {
     use super::*;
 
+    #[test]
+    fn text_before_opening_block_tag_is_separate_paragraph() {
+        for tag in ["div", "p", "li", "h1"] {
+            let body = html_to_body(&format!("Hello<{tag}>world</{tag}>")).unwrap();
+            let texts: Vec<String> = body.paragraphs.iter().map(|p| p.runs.iter().map(|r| r.text.as_str()).collect()).collect();
+            assert_eq!(texts, ["Hello", "world"], "{tag}");
+        }
+    }
+
     #[test]
     fn multibyte_after_ampersand_is_kept() {
         let text = "é".repeat(20);