fix(instanda): set env on go-live, correct secrets docblock, add feed advisory

- F-03: switch_to_live() now sets espinstanda_env=live so environment() actually
  resolves to Live after go-live (was leaving real quotes on the Test endpoint).
- F-04: correct the class-config docblock overstating the at-rest guarantee; it
  only holds when SPG_INSTANDA_KEY is a constant (else the key is self-provisioned
  into the same DB as the ciphertext).
- F-02: add advisory A5 "exactly one active INSTANDA feed" to catch a stray
  test-form feed that also creates quotes.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

wp-content/plugins/esp-instanda-integration/includes/class-go-live.php

@@ -106,9 +106,29 @@ final class Go_Live {
             ['key' => 'A2', 'label' => 'Alert email recipient(s)', 'detail' => $emails !== '' ? $emails : 'None set', 'pass' => $emails !== ''],
             ['key' => 'A3', 'label' => 'Front-end form submit + redirect verified in a browser', 'detail' => $this->ack_detail('espinstanda_frontend_ack'), 'pass' => (bool) get_option('espinstanda_frontend_ack')],
             ['key' => 'A4', 'label' => 'No unresolved failures', 'detail' => $unresolved === 0 ? 'Clean' : "{$unresolved} unresolved", 'pass' => $unresolved === 0],
+            ['key' => 'A5', 'label' => 'Exactly one active INSTANDA feed', 'detail' => $this->feed_summary(), 'pass' => $this->active_feed_count() === 1],
         ];
     }
 
+    /** Count active INSTANDA feeds across all forms (should be exactly one at go-live). */
+    private function active_feed_count(): int {
+        if (!class_exists(__NAMESPACE__ . '\\Instanda_AddOn')) {
+            return 0;
+        }
+        $feeds = Instanda_AddOn::get_instance()->get_feeds();
+        return count(array_filter((array) $feeds, static fn ($f) => !empty($f['is_active'])));
+    }
+
+    private function feed_summary(): string {
+        $n = $this->active_feed_count();
+        if ($n === 1) {
+            return '1 active feed';
+        }
+        return $n === 0
+            ? 'No active feed - the quote form will not push to INSTANDA'
+            : "{$n} active feeds - deactivate all but the canonical quote form (a stray test-form feed also creates quotes)";
+    }
+
     /** @return array{complete:int,total:int,ready:bool} */
     public function readiness(): array {
         $blocking = $this->blocking_items();
@@ -129,6 +149,10 @@ final class Go_Live {
             return false;
         }
         update_option('espinstanda_operating_mode', 'live');
+        // Switching the mode must also select the Live environment, mirroring
+        // return_to_test(); otherwise environment() stays clamped to Test and real
+        // customer quotes would keep hitting the Test endpoint after go-live.
+        update_option('espinstanda_env', 'live');
         update_option('espinstanda_operating_mode_audit', [
             'actor'    => get_current_user_id(),
             'ts'       => current_time('mysql'),