fix(metrics): pick the root disk on the server Metrics page like the Fleet page

The server Metrics page now uses SentinelMetricsClient::rootMountName():
/, else /app/db (Sentinel 1.1.2 and older), else /data/coolify or /data
(Sentinel 1.1.3 and newer). Before, it kept only /, so the disk chart was
empty when Sentinel did not report a / mount.

app/Services/SentinelMetricsClient.php

@@ -184,7 +184,7 @@ class SentinelMetricsClient
      *
      * @param  array<int, array<string, mixed>>  $rows
      */
-    private static function rootMountName(array $rows): ?string
+    public static function rootMountName(array $rows): ?string
     {
         $mounts = array_column($rows, 'mount');
 

app/Traits/HasMetrics.php

@@ -3,6 +3,7 @@
 namespace App\Traits;
 
 use App\Models\Server;
+use App\Services\SentinelMetricsClient;
 use Illuminate\Contracts\Encryption\DecryptException;
 use Illuminate\Support\Facades\Log;
 
@@ -80,7 +81,7 @@ trait HasMetrics
 
     /**
      * Root filesystem usage percentage over time. Disk history interleaves every
-     * mount, so we keep only the root mount before mapping.
+     * mount, so we keep only the root mount (see SentinelMetricsClient::rootMountName()).
      */
     public function getDiskMetrics(int $mins = 5): ?array
     {
@@ -90,7 +91,8 @@ trait HasMetrics
         }
 
         if (array_any($rows, fn ($row) => array_key_exists('mount', $row))) {
-            $rows = array_values(array_filter($rows, fn ($row) => ($row['mount'] ?? null) === '/'));
+            $mount = SentinelMetricsClient::rootMountName($rows);
+            $rows = array_values(array_filter($rows, fn ($row) => ($row['mount'] ?? null) === $mount));
         }
 
         return $this->mapRows($rows, 'usedPercent', $mins);

tests/Unit/Metrics/HasMetricsMappingTest.php

@@ -74,6 +74,16 @@ it('does not use non-root mounts when root disk samples are missing', function (
     expect($double->getDiskMetrics(5))->toBe([]);
 });
 
+it('uses the Sentinel data mount for disk metrics when no root mount is reported', function () {
+    $double = new MetricsMappingDouble;
+    $double->rowsByType['disk'] = [
+        ['time' => 1000, 'mount' => '/boot', 'usedPercent' => 90],
+        ['time' => 1000, 'mount' => '/app/db', 'usedPercent' => 30],
+    ];
+
+    expect($double->getDiskMetrics(5))->toBe([[1000, 30.0]]);
+});
+
 it('supports older disk rows without a mount field', function () {
     $double = new MetricsMappingDouble;
     $double->rowsByType['disk'] = [['time' => 1000, 'usedPercent' => 40]];