Add 10-second error suppression grace period after SPA navigation

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

app/RSpade/Core/Js/Ajax.js

@@ -50,6 +50,14 @@ class Ajax {
                 const error = event.reason;
                 console.error('Uncaught Ajax error:', error);
 
+                // Suppress errors during navigation grace period
+                // After page navigation, pending requests from the old page may error out
+                // These errors are not relevant to the new page
+                if (typeof Spa !== 'undefined' && Spa.is_within_navigation_grace_period()) {
+                    console.log('[Ajax] Suppressing error modal during navigation grace period');
+                    return;
+                }
+
                 // Show error modal for uncaught Ajax errors
                 // In debug mode, use fatal_error() for detailed file/line info
                 if (typeof Modal !== 'undefined') {

app/RSpade/Core/Js/Exception_Handler.js

@@ -160,6 +160,14 @@ class Exception_Handler {
             return;
         }
 
+        // Suppress errors during navigation grace period
+        // After page navigation, pending requests from the old page may error out
+        // These errors are not relevant to the new page
+        if (typeof Spa !== 'undefined' && Spa.is_within_navigation_grace_period()) {
+            console.log('[Exception_Handler] Suppressing error flash during navigation grace period');
+            return;
+        }
+
         // Extract message from Error object or string
         let error_text;
         if (exception instanceof Error) {

app/RSpade/Core/SPA/Spa.js

@@ -43,6 +43,28 @@ class Spa {
     // Flag to track if initial load is complete (for session validation)
     static _initial_load_complete = false;
 
+    // Timestamp of last navigation start - used for error suppression grace period
+    static _navigation_timestamp = 0;
+
+    // Grace period in milliseconds for suppressing errors after navigation
+    static NAVIGATION_GRACE_PERIOD_MS = 10000;
+
+    /**
+     * Check if we're within the navigation grace period
+     *
+     * During the 10 seconds after navigation starts, pending AJAX requests from the
+     * previous page may error out (because their context is gone). These errors should
+     * not be shown to the user as they're not relevant to the new page.
+     *
+     * @returns {boolean} True if within grace period, false otherwise
+     */
+    static is_within_navigation_grace_period() {
+        if (Spa._navigation_timestamp === 0) {
+            return false;
+        }
+        return (Date.now() - Spa._navigation_timestamp) < Spa.NAVIGATION_GRACE_PERIOD_MS;
+    }
+
     /**
      * Disable SPA navigation - all navigation becomes full page loads
      * Call this when errors occur or forms are dirty
@@ -521,6 +543,10 @@ class Spa {
 
         Spa.is_dispatching = true;
 
+        // Record navigation timestamp for error suppression grace period
+        // Errors from previous page's pending requests should be ignored for 10 seconds
+        Spa._navigation_timestamp = Date.now();
+
         try {
             const opts = {
                 history: options.history || 'auto',