feat: catalog shared contracts (Tasks 1-4)

Task 1: Establish catalog identity and atomic file ownership
- CatalogService, CatalogServiceInterface, ModelMetadata DTO
- PdoCatalogRepository with atomic operations, savepoint support
- FOR UPDATE file locks in ascending order, FOR NO KEY UPDATE for metadata
- FK-compatible lock composition documented (spec §6)

Task 2: M3 import & indexing engine delivery layer
- ImportService, ImportWorker with durable collision handling
- SpaceChecker, StreamingHasher, VerifiedCopier, StlValidator
- FileEnumerator, LocalFilesystem, PathSafety
- Console command wiring via ContainerWiringTest

Task 3: Importer integration and repair
- LegacyGuessedImportGroupingAdapter isolates first-directory guessing
- ImportService uses adapter; ImportWorker uses CatalogServiceInterface
- Null owners remain null; DomainException mapped to CATALOG_CONFLICT
- SQL failure after registration/path update with caller sentinel rollback

Task 4: PostgreSQL contention evidence and bounded acceptance
- 6 new PostgresCatalogContractsTest cases with independent sessions
- Generated schemas, 250ms lock timeouts, 5s statement timeouts
- Ascending file locks, FOR SHARE contention, stale-owner rejection
- Rollback/retry, nested transaction survival, root creation contention
- Negative controls: replay FOR UPDATE removal (11 failures), metadata FOR UPDATE (4 FK KEY SHARE timeouts)
- Fresh Docker PostgreSQL 17 / PHP 8.4.26: 473 tests, 2718 assertions, 10 skips, exit 0

All local: 474 tests, 2347 assertions, 54 skips, foundation/lint clean.

src/Indexer/ImportService.php

@@ -5,14 +5,13 @@ declare(strict_types=1);
 namespace MeshVault\Indexer;
 
 use MeshVault\Indexer\Contracts\FileEnumeratorInterface;
-use MeshVault\Repository\CatalogRepositoryInterface;
 use MeshVault\Repository\ImportJobRepositoryInterface;
 use Throwable;
 
 /**
  * Turns a source tree into a durable import job manifest.
  *
- * Grouping policy (explicit, never inferred from file contents): each file is
+ * Legacy guessed grouping (not user-confirmed associations): each file is
  * assigned to the model named after its first directory component below the
  * source root; files sitting directly in the source root join a model named
  * after the source directory itself. Every model lives in a folder of the same
@@ -24,7 +23,7 @@ final readonly class ImportService
     public function __construct(
         private FileEnumeratorInterface $enumerator,
         private ImportJobRepositoryInterface $jobs,
-        private CatalogRepositoryInterface $catalog,
+        private LegacyGuessedImportGroupingAdapter $groupingAdapter,
         private SpaceChecker $space,
         private string $libraryRoot,
     ) {
@@ -59,15 +58,12 @@ final readonly class ImportService
     /** @return list<array<string, mixed>> */
     private function manifest(string $sourcePath, ScanResult $scan): array
     {
-        $models = [];
         $items = [];
         foreach ($scan->files as $file) {
-            $group = $this->group($sourcePath, $file);
-            $models[$group] ??= $this->catalog->ensureModel('/' . $group, $group);
             $items[] = [
                 'source_path' => $file->sourcePath,
                 'size' => $file->size,
-                'model_id' => $models[$group],
+                'model_id' => $this->groupingAdapter->modelFor($sourcePath, $file),
             ];
         }
         // Scan failures become terminal items so the job reports them durably.
@@ -82,13 +78,4 @@ final readonly class ImportService
         }
         return $items;
     }
-
-    private function group(string $sourcePath, ScannedFile $file): string
-    {
-        $parent = trim(str_replace('\\', '/', dirname($file->relativePath)), '/');
-        if ($parent === '' || $parent === '.') {
-            return basename(rtrim(str_replace('\\', '/', $sourcePath), '/'));
-        }
-        return explode('/', $parent)[0];
-    }
 }