Smoke test flag-on showed characters/NPCs disappearing along with
static scenery. Root cause: Task 9 routed all
InstancedMeshRenderer.EnsureUploaded calls through WB. But that
renderer is used for BOTH tiers in production — character per-part
spawn (line 2302, per-instance) AND streaming-loader spawns (lines
5137 + 5155, atlas).
The renderer is tier-blind by design. Tier-routing belongs at the
spawn-callback layer per the spec's data-flow section:
- LandblockSpawnAdapter (Task 11) calls IncrementRefCount per
unique GfxObj — atlas-tier only.
- EntitySpawnAdapter (Task 17) routes through per-instance path
via TextureCache.GetOrUploadWithPaletteOverride.
This commit removes the sentinel pattern + 4 sentinel-skip checks
from InstancedMeshRenderer. Kept the _wbMeshAdapter constructor
parameter (unused for now) so GameWindow's wire-up doesn't shift.
Kept all the real WB pipeline construction in WbMeshAdapter
(it's the substrate routing will use in Week 2).
Verified flag-on === flag-off post-revert.
Plan updated with Adjustment 2 explaining the discovery + correct
architectural placement for routing.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>