ui/map-renderer: clarify rationale for synthetic moved-event type

Expanding the comment so future readers know the `type` field is
informational here — no `pixi-viewport@6` plugin or local listener
switches on it, so picking any literal from the closed union works.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

ui/frontend/src/routes/__debug/map/+page.svelte

@@ -93,8 +93,10 @@
 					handle.viewport.moveCenter(cx, cy);
 					// `MovedEvent.type` is a closed literal union over the
 					// built-in plugin names; `"animate"` is the closest
-					// match for a programmatic move and the renderer's
-					// listeners read only `viewport`.
+					// match for a programmatic move. The renderer's
+					// listeners (and `pixi-viewport@6`'s own plugins)
+					// read only `viewport` — no consumer switches on
+					// `type`, so the choice is informational.
 					handle.viewport.emit("moved", {
 						viewport: handle.viewport,
 						type: "animate",