phase(N.5): retirement amendment — InstancedMeshRenderer + StaticMeshRenderer + WbFoundationFlag deleted

Final cross-cutting review of N.5 found that Task 15's deletion of
mesh_instanced.vert/.frag left InstancedMeshRenderer orphaned —
ACDREAM_USE_WB_FOUNDATION=0 silently rendered terrain+sky only with
no entities. The SHIP commit's "[x] ACDREAM_USE_WB_FOUNDATION=0 still
works" claim was inaccurate.

Resolution: formal retirement of the legacy renderer path within N.5
instead of deferring to N.6.

Deleted:
- src/AcDream.App/Rendering/InstancedMeshRenderer.cs
- src/AcDream.App/Rendering/StaticMeshRenderer.cs
- src/AcDream.App/Rendering/Wb/WbFoundationFlag.cs

GameWindow simplified — capability detection is unconditional, missing
bindless throws NotSupportedException with a clear message at startup.
WbDrawDispatcher + mesh_modern shader load are mandatory after init.
No escape hatch.

GpuWorldState simplified — WbFoundationFlag.IsEnabled guards on
AddLandblock/RemoveLandblock removed; adapter calls are unconditional
when the adapter is non-null.

PendingSpawnIntegrationTests updated — WbFoundationFlag.ForTestsOnly_ForceEnable
static ctor removed (flag is gone; adapter calls are unconditional).

The ApplyLoadedTerrain physics-data loop was also simplified: the
EnsureUploaded sub-loop that fed InstancedMeshRenderer is gone;
_pendingCellMeshes is now explicitly cleared to prevent unbounded
accumulation (the worker thread still populates it, but WB handles
EnvCell geometry through its own pipeline).

Spec §2 Decision 5 + §10 Out-of-Scope updated. Plan ship-amendment
section added. Roadmap updated (N.5 ships with retirement; N.6 scope
narrowed to perf-only). CLAUDE.md "WB integration cribs" updated.
Perf baseline doc updated. WbDrawDispatcher class summary docstring
corrected to describe the as-shipped SSBO + multi-draw-indirect path.
ISSUES.md #51 updated (terrain not in N.5 scope; deferred to N.7).

Bindless support is now a hard requirement. Modern desktop GPUs
universally expose GL_ARB_bindless_texture + GL_ARB_shader_draw_parameters;
if a user hits the NotSupportedException, that's a real bug report
worth investigating, not a silent fallback.

Build: 0 errors, 0 warnings. Tests: 71/71 (Wb+MatrixComposition+TextureCacheBindless filter).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

docs/ISSUES.md

@@ -82,11 +82,12 @@ ground. This is the bug class fixed in
 
 **Sequencing implication:** Phase N.2 (terrain math helpers
 substitution) cannot be shipped in isolation — it must land alongside
-N.5 (visual terrain renderer migration), at which point both physics
-and visual mesh switch to WB's formula together. Roadmap N.2 entry
-flags this dependency.
+visual terrain renderer migration (originally N.5, now moved to N.7
+scope), at which point both physics and visual mesh switch to WB's
+formula together. N.5 shipped entity rendering only; terrain remains
+on acdream's own pipeline through N.7.
 
-**Research needed (when N.5 picks this up):**
+**Research needed (when N.7 picks this up):**
 1. Quantify divergence: run WB's `CalculateSplitDirection` and our
    `IsSplitSWtoNE` across all (lbX, lbY, cellX, cellY) tuples for a
    representative landblock set; record disagreement rate.
@@ -97,8 +98,8 @@ flags this dependency.
    server-authoritative Z within tolerance) is invalidated by the
    formula change.
 
-**Acceptance:** Resolved when N.5 lands and both physics + visual
-mesh use WB's split formula, OR when we decide to keep the AC2D
+**Acceptance:** Resolved when N.7 lands and both physics + visual
+terrain use WB's split formula, OR when we decide to keep the AC2D
 formula and patch WB's renderer in our fork.
 
 ---
@@ -998,8 +999,8 @@ If the coat texture's UVs at the upper region map to texel-bytes whose palette i
 
 **Files (diagnostic env vars committed for next-session reuse):**
 
-- `src/AcDream.App/Rendering/InstancedMeshRenderer.cs:210-275`
-  — `ACDREAM_NO_CULL` env var
+- ~~`src/AcDream.App/Rendering/InstancedMeshRenderer.cs:210-275`
+  — `ACDREAM_NO_CULL` env var~~ (file deleted in N.5 ship amendment)
 - `src/AcDream.App/Rendering/GameWindow.cs` — `ACDREAM_HIDE_PART=N`
   hides specific humanoid part; `ACDREAM_DUMP_CLOTHING=1` dumps
   AnimPartChanges + TextureChanges + per-part Surface chain coverage.