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/TodoCompletedEventHandler.qml

@@ -0,0 +1,31 @@
+// Auto-generated by `bin/console make:bridge:event TodoCompleted`.
+// Listens for `app://event/todo-completed` envelopes published by
+// TodoCompletedSubscriber and re-emits them as a typed QML signal.
+//
+// Drop into a parent component and connect:
+//
+//     TodoCompletedEventHandler {
+//         onTodoCompleted: function(payload) { console.log("hi", payload) }
+//     }
+
+import QtQuick
+import PhpQml.Bridge
+
+Item {
+    id: handler
+
+    /** Emitted when the bridge publishes app://event/todo-completed. */
+    signal todoCompleted(var payload)
+
+    MercureClient {
+        baseUrl: BackendConnection.url
+        token:   BackendConnection.token
+        topics:  ["app://event/todo-completed"]
+
+        onUpdate: function(topic, envelope) {
+            if (topic === "app://event/todo-completed") {
+                handler.todoCompleted(envelope.data)
+            }
+        }
+    }
+}