Fix timestamp regex to accept both Z and timezone offset formats

- Accept both '2024-01-01T12:00:00Z' and '2024-01-01T12:00:00+00:00'
- Fixes test failures on systems with different git timestamp formats

Co-authored-by: Manuel Kießling <manuel@kiessling.net>

Author: cursoragent

tests/Unit/WorkspaceMgmt/GitCliAdapterTest.php

@@ -176,9 +176,9 @@ public function testGetRecentCommitsTimestampIsIso8601(): void
 
         self::assertCount(1, $commits);
 
-        // Verify timestamp is in ISO 8601 format (e.g., 2024-01-01T12:00:00+00:00)
+        // Verify timestamp is in ISO 8601 format (e.g., 2024-01-01T12:00:00+00:00 or 2024-01-01T12:00:00Z)
         $timestamp = $commits[0]->timestamp;
-        self::assertMatchesRegularExpression('/^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}[+-]\d{2}:\d{2}$/', $timestamp);
+        self::assertMatchesRegularExpression('/^\d{4}-\d{2}-\d{2}T\d{2}:\d{2}:\d{2}(Z|[+-]\d{2}:\d{2})$/', $timestamp);
     }
 
     private function runGitCommand(string $command): void