Let one gate decide every AI surface, so switching AI off actually removes all of it

The Tools card adopted the AI scripts on the host check alone, and api/ai.php only
tested AI_ENABLED in front of ask, so a disabled subsystem still had rows to run and
an endpoint that answered.

Plugin/unraid/include/config.php

@@ -268,6 +268,19 @@ function vv_is_ai_host(): bool {
     return vv_detect_host() === 'host1';
 }
 
+// Whether the UI may offer anything AI at all: the right host, with the master switch on. Every
+// AI surface asks this one question — the AI tab, the assistant dock on the Scheduler, and the
+// two AI rows on the Tools card — so AI off means AI gone, not gone from most places.
+//
+// It lives here rather than in include/ai.php because the pages that need it do not all load
+// that file; the Scheduler loads only config.php, and a gate that silently answers false where
+// its definition is missing is worse than no gate. Reads AI_ENABLED directly for the same
+// reason. Fail-closed on anything but the literal "true", matching the conf's own contract.
+function vv_ai_ui_on(): bool {
+    return vv_is_ai_host()
+        && strtolower(trim(vv_conf_vars()['AI_ENABLED'] ?? 'false')) === 'true';
+}
+
 function vv_read_conf_raw(string $filename): string {
     $path = CONF_DIR . '/' . $filename;
     return file_exists($path) ? file_get_contents($path) : '';