fix(vessels): pin the idle-render contract and move the entry to a fragment

- The trailing visibility frame uses the layer's injectable runtime timer and
  is cancelled by resetState as well as disable and destroy.
- An empty-feed regular pass records the camera pose, so later in-cadence
  frames do not keep scheduling trailing frames.
- New renderGovernor.test.mjs: a parked camera schedules nothing, a stopped
  camera gets exactly one trailing frame and no self-wake, a forced pass
  requests its frame, destroy cancels the timer.
- The CHANGELOG entry moves to changelog.d/871-vessels-idle-render.md; docs
  say the hold also covers vessels dimmed under a live target.

src/layers/vessels/lifecycle.js

@@ -125,7 +125,7 @@ export function createLifecycle({
     state.interactionHandlerFactory = null;
     state.interactionKeyTarget = null;
     state.preRenderRemover = null;
-    state.trailingVisibilityTimer = null;
+    components.rendering.cancelTrailingVisibilityPass();
     state.lastVisibilityUpdate = 0;
     state.lastFocusUpdate = 0;
     state.activeFocusCount = 0;