Render light markdown in chat messages

Bodies were printed verbatim, so an agent's **bold**, `code`, or
[link](https://...) showed as literal punctuation — the opposite of
people talking. Render the inline markdown agents and humans actually
use in chat into React nodes, composed around the existing @mention
highlighting.

Links are restricted to http(s) and nothing is ever set as raw HTML
(no dangerouslySetInnerHTML), so a message body can never inject markup
or a javascript: URL. A plain message still comes back as one string.

AgentCompany-New/src/renderer/src/pages/chat/ChatMessageRow.tsx

@@ -132,7 +132,7 @@ export function ChatMessageRow({
 }
 
 function renderBody(body: string, mentions: ChatMentionRecord[], context: MessageContext): ReactNode {
-  if (mentions.length === 0) return body;
+  if (mentions.length === 0) return formatInline(body, "b");
   const parts: ReactNode[] = [];
   const ordered = [...mentions].sort((a, b) => a.offsetStart - b.offsetStart);
   let lastIndex = 0;
@@ -143,7 +143,7 @@ function renderBody(body: string, mentions: ChatMentionRecord[], context: Messag
     }
     const token = body.slice(mention.offsetStart, mention.offsetEnd);
     if (!token.startsWith("@")) throw new Error("Message mention token is invalid.");
-    if (mention.offsetStart > lastIndex) parts.push(body.slice(lastIndex, mention.offsetStart));
+    if (mention.offsetStart > lastIndex) parts.push(...formatInline(body.slice(lastIndex, mention.offsetStart), `s${lastIndex}`));
     const label = mentionLabel(mention, context);
     parts.push(
       <span
@@ -155,10 +155,34 @@ function renderBody(body: string, mentions: ChatMentionRecord[], context: Messag
     );
     lastIndex = mention.offsetEnd;
   }
-  if (lastIndex < body.length) parts.push(body.slice(lastIndex));
+  if (lastIndex < body.length) parts.push(...formatInline(body.slice(lastIndex), `s${lastIndex}`));
   return parts;
 }
 
+/**
+ * Renders the light markdown agents and people use in chat — **bold**, *italic*,
+ * `code`, and [text](https://link) — into React nodes. Links are restricted to
+ * http(s) and nothing is ever set as raw HTML, so message bodies stay inert. A
+ * message with no markdown comes back as a single plain string.
+ */
+function formatInline(text: string, keyPrefix: string): ReactNode[] {
+  const pattern = /(\*\*([^*\n]+)\*\*|\*([^*\n]+)\*|`([^`\n]+)`|\[([^\]\n]+)\]\((https?:\/\/[^\s)]+)\))/g;
+  const nodes: ReactNode[] = [];
+  let lastIndex = 0;
+  let token = 0;
+  for (let match = pattern.exec(text); match; match = pattern.exec(text)) {
+    if (match.index > lastIndex) nodes.push(text.slice(lastIndex, match.index));
+    const key = `${keyPrefix}-${token++}`;
+    if (match[2] !== undefined) nodes.push(<strong key={key}>{match[2]}</strong>);
+    else if (match[3] !== undefined) nodes.push(<em key={key}>{match[3]}</em>);
+    else if (match[4] !== undefined) nodes.push(<code key={key} className="mono" style={{ background: "var(--panel-3)", padding: "1px 5px", borderRadius: 4, fontSize: "0.92em" }}>{match[4]}</code>);
+    else nodes.push(<a key={key} href={match[6]} target="_blank" rel="noreferrer" style={{ color: "var(--accent)" }}>{match[5]}</a>);
+    lastIndex = pattern.lastIndex;
+  }
+  if (lastIndex < text.length) nodes.push(text.slice(lastIndex));
+  return nodes;
+}
+
 function mentionLabel(mention: ChatMentionRecord, context: MessageContext): string {
   if (mention.targetType === "employee") {
     const employee = context.employees.find((item) => item.id === mention.targetId);