feat(dashboard): close legacy parity gaps

apps/dashboard/src/features/conversations/processed-user-lookup.tsx

@@ -0,0 +1,28 @@
+import { useState } from 'react';
+import { useProcessedPostsQuery } from './conversation-queries.js';
+
+export function ProcessedUserLookup() {
+  const [input, setInput] = useState('');
+  const [username, setUsername] = useState('');
+  const postsQuery = useProcessedPostsQuery(username);
+
+  return (
+    <section aria-labelledby="processed-user-heading" className="new-conversation-panel">
+      <h2 id="processed-user-heading">Processed user lookup</h2>
+      <form onSubmit={(event) => { event.preventDefault(); setUsername(input.trim().replace(/^u\//i, '')); }}>
+        <label htmlFor="processed-user">Lookup Reddit username</label>
+        <input id="processed-user" onChange={(event) => setInput(event.target.value)} value={input} />
+        <button disabled={input.trim().length === 0} type="submit">Look up user</button>
+      </form>
+      {postsQuery.isPending && username ? <p role="status">Looking up processed posts…</p> : null}
+      {postsQuery.isError ? <p role="alert">{postsQuery.error.message}</p> : null}
+      {postsQuery.data ? (
+        postsQuery.data.length === 0 ? <p>No processed posts found for u/{username}.</p> : (
+          <ol aria-label={`Processed posts for u/${username}`}>
+            {postsQuery.data.map((post) => <li key={post.id}><strong>{post.title}</strong><span>r/{post.subreddit} · {post.messageSent ? 'Message sent' : post.error ?? 'Processed'}</span></li>)}
+          </ol>
+        )
+      ) : null}
+    </section>
+  );
+}