Add session list refresh with server cache bypass

useSession now exposes a refreshSessions() callback that fetches
/api/sessions?refresh=1. The sessions route checks for the refresh
query parameter and resets the cache timestamp to zero, forcing a
fresh scan of ~/.claude/projects/ on the next request.

This enables users to pick up new sessions without restarting the
server or waiting for the 30-second cache to expire.

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

src/server/routes/sessions.ts

@@ -19,8 +19,11 @@ async function getCachedSessions(): Promise<SessionEntry[]> {
   return cachedSessions;
 }
 
-sessionsRouter.get("/", async (_req, res) => {
+sessionsRouter.get("/", async (req, res) => {
   try {
+    if (req.query.refresh === "1") {
+      cacheTimestamp = 0;
+    }
     const sessions = await getCachedSessions();
     res.json({ sessions });
   } catch (err) {