feat(lsp): add list.removeCheckbox and link.catUrl commands

removeCheckbox strips the `[ ]` marker (plus its trailing space) from
the current item or every item in the list. catUrl returns the
`file://` URL of the current page's HTML export, mirroring vimwiki's
:VimwikiCatUrl.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

crates/nuwiki-lsp/tests/commands_lists.rs

@@ -192,6 +192,41 @@ fn change_symbol_whole_list_rewrites_every_item() {
     assert!(texts.contains(&"3."));
 }
 
+// ===== removeCheckbox =====
+
+#[test]
+fn remove_checkbox_strips_single_item() {
+    let src = "- [ ] task\n- [X] done\n";
+    let ast = parse(src);
+    let edit = ops::remove_checkbox_edit(src, &ast, &uri(), 0, false, true).expect("edit");
+    let edits = &edit.changes.unwrap()[&uri()];
+    assert_eq!(edits.len(), 1);
+    assert_eq!(edits[0].new_text, "");
+    // Removes `[ ] ` — columns 2..6 on the first line.
+    assert_eq!(edits[0].range.start.line, 0);
+    assert_eq!(edits[0].range.start.character, 2);
+    assert_eq!(edits[0].range.end.character, 6);
+}
+
+#[test]
+fn remove_checkbox_whole_list_strips_every_item() {
+    let src = "- [ ] a\n- [X] b\n- [-] c\n";
+    let ast = parse(src);
+    let edit = ops::remove_checkbox_edit(src, &ast, &uri(), 0, true, true).expect("edit");
+    let edits = &edit.changes.unwrap()[&uri()];
+    assert_eq!(edits.len(), 3);
+    for e in edits {
+        assert_eq!(e.new_text, "");
+    }
+}
+
+#[test]
+fn remove_checkbox_none_without_checkbox() {
+    let src = "- plain item\n";
+    let ast = parse(src);
+    assert!(ops::remove_checkbox_edit(src, &ast, &uri(), 0, false, true).is_none());
+}
+
 // ===== changeLevel =====
 
 #[test]
@@ -231,6 +266,7 @@ fn commands_list_includes_cluster_a() {
     let names: Vec<&str> = nuwiki_lsp::commands::COMMANDS.to_vec();
     for name in [
         "nuwiki.list.removeDone",
+        "nuwiki.list.removeCheckbox",
         "nuwiki.list.renumber",
         "nuwiki.list.changeSymbol",
         "nuwiki.list.changeLevel",