fix(editor): trim trailing whitespace from getMarkdown() output

ProseMirror always keeps an empty paragraph at the document end (schema
requires "block+"), which getMarkdown() serializes as trailing "\n\n".
Without trimming, each save→reload cycle adds an extra empty line.

Centralize the trim in ContentEditor (both onUpdate callback and ref
getMarkdown), removing redundant .replace() calls from comment-input,
reply-input, and comment-card.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

apps/web/features/editor/content-editor.tsx

@@ -109,7 +109,11 @@ const ContentEditor = forwardRef<ContentEditorRef, ContentEditorProps>(
         if (!onUpdateRef.current) return;
         if (debounceRef.current) clearTimeout(debounceRef.current);
         debounceRef.current = setTimeout(() => {
-          onUpdateRef.current?.(ed.getMarkdown());
+          // Trim trailing whitespace: ProseMirror always keeps an empty
+          // paragraph at the document end (schema: "block+"), which
+          // getMarkdown() serializes as trailing "\n\n". Without trimming,
+          // each save→reload cycle would add an extra empty line.
+          onUpdateRef.current?.(ed.getMarkdown().replace(/(\n\s*)+$/, ""));
         }, debounceMs);
       },
       onBlur: () => {
@@ -175,7 +179,7 @@ const ContentEditor = forwardRef<ContentEditorRef, ContentEditorProps>(
     }, [editor, editable, defaultValue]);
 
     useImperativeHandle(ref, () => ({
-      getMarkdown: () => editor?.getMarkdown() ?? "",
+      getMarkdown: () => editor?.getMarkdown().replace(/(\n\s*)+$/, "") ?? "",
       clearContent: () => {
         editor?.commands.clearContent();
       },

apps/web/features/issues/components/comment-card.tsx

@@ -131,10 +131,7 @@ function CommentRow({
 
   const saveEdit = async () => {
     if (cancelledRef.current) return;
-    const trimmed = editEditorRef.current
-      ?.getMarkdown()
-      ?.replace(/(\n\s*)+$/, "")
-      .trim();
+    const trimmed = editEditorRef.current?.getMarkdown()?.trim();
     if (!trimmed || trimmed === (entry.content ?? "").trim()) {
       setEditing(false);
       return;
@@ -300,10 +297,7 @@ function CommentCard({
 
   const saveEdit = async () => {
     if (cancelledRef.current) return;
-    const trimmed = editEditorRef.current
-      ?.getMarkdown()
-      ?.replace(/(\n\s*)+$/, "")
-      .trim();
+    const trimmed = editEditorRef.current?.getMarkdown()?.trim();
     if (!trimmed || trimmed === (entry.content ?? "").trim()) {
       setEditing(false);
       return;

apps/web/features/issues/components/comment-input.tsx

@@ -23,7 +23,7 @@ function CommentInput({ issueId, onSubmit }: CommentInputProps) {
   };
 
   const handleSubmit = async () => {
-    const content = editorRef.current?.getMarkdown()?.replace(/(\n\s*)+$/, "").trim();
+    const content = editorRef.current?.getMarkdown()?.trim();
     if (!content || submitting) return;
     setSubmitting(true);
     try {

apps/web/features/issues/components/reply-input.tsx

@@ -56,7 +56,7 @@ function ReplyInput({
   };
 
   const handleSubmit = async () => {
-    const content = editorRef.current?.getMarkdown()?.replace(/(\n\s*)+$/, "").trim();
+    const content = editorRef.current?.getMarkdown()?.trim();
     if (!content || submitting) return;
     setSubmitting(true);
     try {