Render streamed assistant responses as Markdown

frontend/src/ai/style.css

@@ -82,6 +82,60 @@
   line-height: 24px;
   font-weight: 400;
 }
+.ai-markdown {
+  min-width: 0;
+  font-size: 14px;
+  line-height: 24px;
+}
+.ai-markdown .markstream-react {
+  color: var(--ink);
+  font-family: inherit;
+  font-size: inherit;
+  line-height: inherit;
+}
+.ai-markdown :is(h1, h2, h3, h4, h5, h6) {
+  font-size: 16px;
+  line-height: 24px;
+  font-weight: 600;
+  margin: 16px 0 8px;
+}
+.ai-markdown :is(p, ul, ol, blockquote, pre, table) {
+  margin-top: 8px;
+  margin-bottom: 8px;
+}
+.ai-chat .ai-markdown .markstream-react pre[data-markstream-pre] {
+  font-size: 12px;
+  max-width: 100%;
+  overflow-x: auto;
+  white-space: pre;
+  padding: 12px;
+  border: 1px solid var(--line);
+  border-radius: 6px;
+  background: var(--canvas);
+}
+.ai-markdown code {
+  font-size: 12px;
+}
+.ai-markdown table {
+  display: block;
+  max-width: 100%;
+  overflow-x: auto;
+  border-collapse: collapse;
+}
+.ai-markdown :is(th, td) {
+  padding: 6px 10px;
+  border: 1px solid var(--line);
+  white-space: nowrap;
+}
+.ai-markdown a {
+  color: var(--accent);
+  text-decoration: underline;
+}
+.ai-markdown blockquote {
+  border-left: 3px solid var(--line);
+  padding-left: 12px;
+  color: var(--muted);
+}
 .ai-message.user .ai-text {
   background: var(--canvas);
   padding: var(--space-3);