Fix import status regression from appload 404 + tighten upgrade tests

- itemImport: check response.ok in fetchAppDetails so a genuine 404
  (from the appload return-type fix) is reported as 'Failed to find app
  id' instead of being parsed as a successful import; applied to the
  source and the committed compiled bundle.
- phpunit.xml: point the schema URL at 12.5 to match the installed
  PHPUnit 12.5.x.
- ColorHelpersTest: exercise the get_brightness() non-hex stripping the
  test name promised (interior separators), which the prior assertion
  never covered.

phpunit.xml

@@ -1,5 +1,5 @@
 <?xml version="1.0" encoding="UTF-8"?>
-<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/11.5/phpunit.xsd" bootstrap="vendor/autoload.php" colors="true" cacheDirectory=".phpunit.cache">
+<phpunit xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="https://schema.phpunit.de/12.5/phpunit.xsd" bootstrap="vendor/autoload.php" colors="true" cacheDirectory=".phpunit.cache">
   <testsuites>
     <testsuite name="Unit">
       <directory suffix="Test.php">./tests/Unit</directory>

public/js/app.js

@@ -4484,6 +4484,9 @@ var fetchAppDetails = function fetchAppDetails(appId) {
       app: appId
     })
   }).then(function (response) {
+    if (!response.ok) {
+      return Promise.reject(new Error("Failed to find app id: ".concat(appId)));
+    }
     return response.json();
   });
 };

resources/assets/js/itemImport.js

@@ -92,7 +92,16 @@ const fetchAppDetails = (appId) => {
       "Content-Type": "application/json",
     },
     body: JSON.stringify({ app: appId }),
-  }).then((response) => response.json());
+  }).then((response) => {
+    // A missing app now returns a genuine 404 (see ItemController::appload).
+    // fetch() does not reject on 4xx, so surface it as a rejection here to
+    // keep importItems reporting "Failed to find app id" rather than treating
+    // the {"error":...} body as a successful import.
+    if (!response.ok) {
+      return Promise.reject(new Error(`Failed to find app id: ${appId}`));
+    }
+    return response.json();
+  });
 };
 
 /**

tests/Unit/helpers/ColorHelpersTest.php

@@ -35,6 +35,12 @@ class ColorHelpersTest extends TestCase
     {
         // A value without the leading # must decode identically.
         $this->assertEqualsWithDelta(255, get_brightness('ffffff'), 0.0001);
+
+        // Interior non-hex separators (the "other non-hex" in the name) must be
+        // stripped before decoding, so these normalise to ffffff. If the
+        // preg_replace were dropped these would decode to a different value.
+        $this->assertEqualsWithDelta(255, get_brightness('#ff:ff:ff'), 0.0001);
+        $this->assertEqualsWithDelta(255, get_brightness('ff-ff-ff'), 0.0001);
     }
 
     public function test_get_brightness_weights_channels_per_luma_formula(): void