P3.1: batch processing foundation — BatchService + auto-attach + 3 enum cases + 13 tests

[sjelfull]

P3.1: BatchService foundation — open/close/run API for grouping audit rows

Adds BatchService, the core infrastructure for grouping related audit rows under a parent record. A "batch" is an audit row with event BatchStarted/BatchCompleted/BatchFailed that acts as a parent for all rows recorded while the batch is open. The service is the foundation for P3.2 (ResaveElements), P3.3 (CP UI), and P3.4 (Feed Me).

Auto-attachment is wired into AuditRecorder::record(): after the overrides loop and before EVENT_BEFORE_RECORD, if BatchService::currentBatchId() is non-null and $record->parentId is null, the recorder sets the parent automatically. Callers don't need to know about batches — any audit row recorded while a batch is open inherits the parent ID.

What changed

• src/services/BatchService.php (new, 243 LOC) — open(string $title, array $metadata = []) opens a batch and returns its ID; close(int $batchId, ?string $summary, bool $failed) closes it; run(string $title, callable $callback) wraps open/close around a callback; currentBatchId() returns the active batch ID or null.
• src/events/BatchStartedEvent.php (new, 20 LOC) — event fired after a batch row is persisted. Observational only (not cancellable).
• src/events/BatchEndedEvent.php (new, 25 LOC) — event fired after a batch is closed. Carries $failed flag.
• src/enums/AuditEvent.php (+5 LOC) — adds BatchStarted, BatchCompleted, BatchFailed cases.
• src/services/AuditRecorder.php (+9 LOC) — auto-attach hook: sets $record->parentId from currentBatchId() when not already set.
• src/Audit.php (+3 LOC) — registers BatchService in the service container.
• src/translations/en/audit.php (+5 entries) — batch state labels.
• tests/Feature/BatchServiceTest.php (new, 304 LOC, +13 tests) — covers open/close/run, auto-attach, nested batch behavior, event firing, and failure path.
• tests/Feature/EnumCoverageTest.php — updated to include the 3 new enum cases.

Tests

• +13 tests, +BatchService coverage
• ECS clean
• PHPStan clean
• Fresh-DB green

Stacked on

p2.9-real-api-tests (#115)

[sjelfull]

This change is part of the following stack:

• Phase 1.1 — Foundation: AuditEvent enum + JSON snapshot migration #90
  • Phase 1.2 — Core services: AuditRecorder + FieldDiffService + HandlerRegistry #91
    • Phase 1.3 — Field handlers: 15 handlers for native + third-party fields #92
      • Phase 1.4 — Project config tracking: 8 config areas #93
        • Phase 1.5 — UI: DiffRenderer + 20 Twig templates + asset bundle #94
          • Phase 1.6 — Tests: migration + integration + enum coverage (+19 tests) #95
            • Phase 2.1 — Decompose AuditService: ElementHandler, UserHandler, UserGroupHandler #96
              • Phase 2.2 — Decompose AuditService: Schema/Route/Backup/Plugin/Settings handlers #97
                • Phase 2.3 — Repoint event wiring from AuditService to handler services #98
                  • Phase 2.4 — Migrate Pest tests from AuditModel::EVENT_* to AuditEvent enum #99
                  • Phase 2.5 — CI: PHP 8.2/8.3/8.4 matrix + v3 branch trigger #111
                  • Phase 3.0 — Docs: ship escape hatch (filter-records + getting-started + events-and-recording) #110
                  • P2.6: drop @deprecated AuditService delegators, move @internal helpers to AuditRecorder #112
                  • P2.7: drop @deprecated EVENT_/USER_ string constants from AuditModel, migrate to AuditEvent::Xxx->value #113
                  • P2.8: strip section-divider banners and boilerplate file/class headers #114
                  • P2.9: convert tests to exercise real Craft APIs instead of synthetic event objects #115
                  • P3.1: batch processing foundation — BatchService + auto-attach + 3 enum cases + 13 tests #116 ◀
                  • P3.2: migrate ResaveElements to BatchService — kills cache-key concurrency bug #117
                  • P3.4: Feed Me bake-in — auto-batch each feed import via EVENT_BEFORE/AFTER_PROCESS_FEED #119
                  • P3.3: CP UI — expandable indented batch children in audit log index #120
                  • P3.5: Feed Me integration tests — real class-string event dispatch verified #121
                  • P3.6: Fix snapshot column double-JSON-encoding (FRE-239) #122
                  • P3.7: Stack-wide comment cleanup pass #123

_{Change managed by git-spice.}