wip(assembler): M1 repair round -- raised block and cliff fixed; native 7x faster than legacy

Luna, M1 repair round: the rectangular raised block and the broken cliff shared one cause,
a type-2 solid AABB in the generated plan; it is now a tapered, terrain-following shelf, and
a negative-control audit catches the old box behaviour; seam classification check passes.
Bound audit 298 boxes / 8,046 samples, 0 misses. Evaluator and 120-tile density/mesh/payload/
topology hashes identical at W1/W8/W16. Cave regression: walkability 5,642/5,642, 64/64 tiles.
Legacy mismatch unchanged (0 biome mismatches, 18.14% signs).
Speed (matched workloads): 120-tile full detail 0.089 s native vs 0.625 s legacy; 529-tile
clipmap 3.858 s vs 11.687 s -- 2.29 s above the ~1.57 s aim; LOD8 dominates (165 unknown
tiles, 13.27 M field calls, 10.88 M column-cache misses).
My capture review: coast matches legacy closely; surface clean but a dark flat slab on the far
horizon; cliff shelf renders as a stack of thin plates with back faces showing (sub-voxel
shelf thickness suspected).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01MmSoF64BbRFmk9C3p1VsBJ

Standalone/Research/WorldAssemblerM1/round3/performance/coast-legacy.txt

@@ -0,0 +1,11 @@
+[ProcessControls] priority_class=Normal priority_source=argument affinity_mask=0xFFFF affinity_source=argument requested_affinity=0xFFFF system_affinity=0xFFFF
+[ColdTimeline] stage=owner_data_load begin_ms=0.056
+[ColdTimeline] stage=owner_data_load end_ms=15.889
+Standalone clip override: exported radius=6 (112 m cube) -> radius=1 (32 m LOD0 cube), voxel size=25 cm.
+[StreamBenchmarkConfig] clip_radius=1 lod0_cube=32m voxel=25cm fullres_levels=2 max_level_filter=1 workers=16 full_detail_tiles=120 desired_tiles=120 variant=base uv=full colors=full material_groups=full hash=off
+[StreamFullDetail] wall=0.634s generated=120/120 resident_tiles_cpu_only=1 hash=off
+[PlayerNeighborhood] lod0_tiles=27/27 mesh_ready=0.276s collision_cook=unavailable_in_standalone
+[StreamFullClipmap] wall=0.634s generated=120/120 worker_sum=9.572s worker_busy=94.4% worker_idle=5.6% payload_alloc=3.55MiB viewer_output=1.78MiB tiles=120 hash=off
+[StreamCacheUse] hits=0 requested=120
+[StreamLevel] lod=0 tiles=64 samples=2.744M worker_sum=4.696s first_ready=0.066s complete=0.444s worker_busy=66.2% payload_alloc=0.40MiB viewer_output=0.20MiB vertices=4695 indices=23523 hash=off
+[StreamLevel] lod=1 tiles=56 samples=2.401M worker_sum=4.876s first_ready=0.245s complete=0.631s worker_busy=48.3% payload_alloc=3.15MiB viewer_output=1.57MiB vertices=35355 indices=185238 hash=off