Instanced plant kinds (trees/grass/flowers) never cleared their dirty
marks: FloorElevationSystem deliberately leaves the mark for kinds with
a def.system, expecting that system to clear it after its own work, but
InstancedKindSystem never participated in the dirty protocol. The marks
lived forever, hasPendingSceneBuildWork() never went false, and the
Viewer's scene-ready signal stalled at SCENE_READY_MAX_WAIT_FRAMES on
every plant-containing scene — measured on the headless bake worker as
~190s (180 frames x ~1s SwiftShader frames) of pure cap-wait per bake.
Clear the marks in a priority-2 useFrame pass: after the priority-1
floor-elevation lift in the same frame, and only for nodes whose proxy
is registered (instances rebuild synchronously from the store, so a
rendered node is already built). Validated by baking Wawa House
locally: settle 22.5s -> 11.6s (the remainder is genuine asset
loading), exported GLB byte-identical with and without the fix.
Co-authored-by: Claude Fable 5 <noreply@anthropic.com>
