v0.2.0 (7/N): make:bridge:event maker

Implements PLAN.md §8's third makers-table row. Single-command path
from a PHP domain event to a QML signal-handler:

  - src/Event/<Name>Event.php — readonly value object stub
  - src/EventSubscriber/<Name>Subscriber.php — listens to the event,
    republishes via PublisherInterface on app://event/<kebab-name>
    with op:"event"
  - {qml_path}/<Name>EventHandler.qml — MercureClient bound to the
    topic, re-emits the envelope's data as a typed signal

Stub uses an `array $payload` field so the user can substitute typed
properties for whatever shape they need. Subscriber example uses the
PublisherInterface contract from chunk 1; QML stub uses MercureClient
+ BackendConnection both already shipping.

Wired into services.yaml's when@dev block (autoconfigure picks up
maker.command tag, same pattern as existing BridgeResourceMaker /
BridgeWindowMaker). Three new snapshot baselines plus a snapshot
runner extension exercising the new maker against the same Todo /
TodoCompleted naming the existing baselines use.

End-to-end verified locally: maker output matches baselines, dev
container compiles, listing make:bridge:* shows the new command.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

framework/php/tests/snapshot/TodoCompletedEvent.php

@@ -0,0 +1,21 @@
+<?php
+
+declare(strict_types=1);
+
+namespace App\Event;
+
+/**
+ * Domain event published on `app://event/todo-completed` by
+ * TodoCompletedSubscriber.
+ *
+ * Auto-generated stub — replace the `payload` field with typed
+ * properties matching the event you actually fire.
+ */
+final readonly class TodoCompletedEvent
+{
+    public function __construct(
+        /** @var array<string, mixed> */
+        public array $payload = [],
+    ) {
+    }
+}