feat: establish catalog identity and atomic file ownership

tests/Unit/Catalog/ManagedPathTest.php

@@ -0,0 +1,55 @@
+<?php
+
+declare(strict_types=1);
+
+namespace MeshVault\Tests\Unit\Catalog;
+
+use InvalidArgumentException;
+use MeshVault\Catalog\ManagedPath;
+use PHPUnit\Framework\Attributes\DataProvider;
+use PHPUnit\Framework\TestCase;
+
+final class ManagedPathTest extends TestCase
+{
+    #[DataProvider('validPaths')]
+    public function testPreservesCanonicalSpelling(string $path): void
+    {
+        self::assertSame($path, ManagedPath::validate($path));
+    }
+
+    public static function validPaths(): array
+    {
+        return [['part.stl'], ['Folder/模型 A.STL'], ['a/.hidden'], ['a/space inside.stl']];
+    }
+
+    #[DataProvider('invalidPaths')]
+    public function testRejectsAliases(string $path): void
+    {
+        $this->expectException(InvalidArgumentException::class);
+        ManagedPath::validate($path);
+    }
+
+    public static function invalidPaths(): array
+    {
+        return array_map(static fn (string $path): array => [$path], [
+            '', '/a', '//server/a', 'C:/a', 'C:a', 'a\\b', "a\0b", 'https://host/a',
+            'file:a', 'a//b', 'a/', '.', '..', './a', 'a/../b', 'a/./b',
+        ]);
+    }
+
+    public function testPlatformSpecificRestrictions(): void
+    {
+        foreach (['a/b.', 'a/b ', 'a/b:c'] as $path) {
+            if (PHP_OS_FAMILY === 'Windows') {
+                try {
+                    ManagedPath::validate($path);
+                    self::fail('Expected Windows alias rejection');
+                } catch (InvalidArgumentException) {
+                    self::assertTrue(true);
+                }
+            } else {
+                self::assertSame($path, ManagedPath::validate($path));
+            }
+        }
+    }
+}