ui: detect outdated daemon via WailsUIReady probe

Add a no-op WailsUIReady RPC the UI probes once at startup. A reachable
daemon that returns Unimplemented predates this UI and is too old to
drive it; the probe distinguishes that from an unreachable daemon. On an
outdated daemon the UI fires a localized OS notification, since the main
window may not open to show an in-app error.

Proto regenerated with protoc 33.1 to keep the v6.33.1 header.

client/ui/frontend/src/lib/compat.ts

@@ -0,0 +1,19 @@
+import { Compat } from "@bindings/services";
+
+let cached: boolean | null = null;
+
+/**
+ * isDaemonCompatible probes whether the running daemon implements the WailsUIReady
+ * RPC. A false result means the daemon predates this UI (Unimplemented) and is too
+ * old to drive it. The Go side returns an error instead when the daemon is simply
+ * unreachable, so a throw here is NOT an outdated daemon — treat it as "unknown"
+ * and let the normal connection flow report it.
+ *
+ * The result is cached for the session: daemon identity does not change without a
+ * UI restart, and a freshly started daemon is reachable again under the same socket.
+ */
+export async function isDaemonCompatible(): Promise<boolean> {
+    if (cached !== null) return cached;
+    cached = await Compat.DaemonReady();
+    return cached;
+}