wip(assembler): M3 round 3 -- separated islands + Unreal island route (owner build 18:46)

Islands read as separate (91.89% open sky at mid-height), underside cavity closed,
rim teeth were capture shading. Island manifest import + BuildHost proof passed on the
pre-cache tree; M1 SurfaceWorld and M2 V1/V2 gates passed.

Known open: final XY-column cache compiled in the owner build but is unverified;
island LOD0 p95 ~155 ms misses the 133 ms sprint deadline (legacy ~43 ms); the island
manifest only fits the BuildHost fixture layout (owner's world: Core init fails,
empty world) -> round 4 builds plans inside Unreal.

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

Standalone/DESIGN_WORLD_ASSEMBLER.md

@@ -542,6 +542,55 @@ what the shape list alone misses: site selection, cluster connectivity, landings
 route. The support ranges do not promise that every roll is pretty or walkable; measurement rejects
 bad candidates and records which constraint failed.
 
+#### M3 round 2 — look pass and standalone gates
+
+The legacy settings describe a stochastic site process, not a fixed island count: `IslandDensity=0.5`
+is the chance that each hashed XY cell exists. The owner settings are spacing 112 legacy voxels,
+radii 24–48 legacy voxels, thickness ratio 0.6, vertical jitter/top flatten 0.6, roughness 3,
+blend 6 and boundary seal 4. The production legacy field uses 12.5 cm voxels and Core uses 25 cm, so
+the round-2 Core recipe halves length-valued settings: 56 spacing, 12–24 radii, 1.5 roughness, 3
+blend, 2 seal and 6.3 contour warp. Those values preserve 14 m spacing and 3–6 m radii under the
+production source scale. The legacy struct's radius comment instead assumes 25 cm, and the frozen
+probe metadata reports 25 cm while production `Source` and the plugin `CLAUDE.md` report 12.5 cm.
+The next round must reconcile that fixture metadata before publishing the importer contract.
+
+Geometry version 2 adds a broad crust and 3–4 deterministic tapering root lobes per island. Its
+measured total depth is 0.75 of island diameter; the old thin profile control measures 0.30 and is
+rejected by the 0.70 thickness gate. Full bounded roughness remains on cliffs and roots, while top
+detail is reduced where the route needs stable footing. The three primary islands guarantee an
+entrance-to-exit route; density 0.5 selected one optional side island for this seed, giving four
+islands and three sharp-tag-ready arched spans. The side island is not part of the route.
+
+[`M3 Round 2 report`](Research/WorldAssemblerM3/Round2/REPORT.md) records the five matched views,
+owner-parameter conversion, the full run ledger, and Round 3 delivery plan. The contact sheet is
+[`contact_sheet.jpg`](Research/WorldAssemblerM3/Round2/results/captures/contact_sheet.jpg). Bounds
+had zero misses, the route passed 254 capsule centers and 69,088 field samples, the raised-route and
+thin-pad controls failed as intended, and W1/W8/W16 field hashes matched. On the same 32,768 physical
+query locations, Core took 38.06 ms versus 64.64 ms for the legacy evaluator. The local sample still
+contains 10.6× as many native solid points (1,380 vs 130), due to the guaranteed route backbone and
+deeper root profile; this is a known local density difference, not an occupancy-parity claim.
+
+#### M3 round 3 — Unreal delivery plan
+
+1. Resolve the legacy/Core voxel-scale conflict using the production field constant and the owner
+   snapshot producer; record a single conversion rule in the imported manifest and its preview notes.
+2. Add the floating-island recipe and plan to the existing optional `world_assembly` import pattern.
+   Parse through `ResolvedWorldSnapshot::FromJson`, validate recipe/plan hashes and stable feature
+   IDs, and reject malformed or scale-mismatched payloads before generation.
+3. Prove the imported plan in a null-RHI BuildHost commandlet. Check the canonical hashes and W1/W8/W16
+   queries, then compare generated tiles against the reviewed standalone field without changing the
+   existing Core world or SurfaceWorld hashes.
+4. Carry island and sharp-tag-ready span IDs into the feature-aware mesher path. Audit same-LOD and
+   LOD0/LOD1 borders around the crust, roots and arch landings.
+5. Cook the rendered collision, trace it on the Pawn channel, and capsule-sweep the same serialized
+   route. Compare collision support points to analytic Core support at the island tops and spans.
+6. Hand the owner the manifest, five-view sheet, import steps, route coordinates, and collision
+   results. Use a duplicated test settings asset for preview only after the owner authorizes project
+   asset work; keep shipped assets untouched during the standalone proof.
+
+Water remains a separate fixed-season body and is not part of the round-2 field or the round-3
+collision claim.
+
 ## E. Milestones that end in owner-visible artifacts
 
 These estimates are engineering rounds, not elapsed-time promises. Each milestone ends with a
@@ -551,7 +600,7 @@ standalone viewer/contact sheet, data report or playable inspection the owner ca
 |---|---:|---|---|
 | M1 — sharp-mesher decision spike | 2 rounds | 25 cm contact sheet of corner, one-metre step, cliff ledge and doorway: current MC beside feature-aware output; include LOD/tile seam and collision overlays | Measure surface error, normal splits, determinism and seam behavior before building architectural recipes on top |
 | M2 — SurfaceWorld native vertical slice | 3 rounds | Matched-camera native surface with two biomes, a coast/beach, cliff/overhang, cap, route markers and timing beside the exact legacy bridge | No missed bound; the matched full-view workload materially beats the 23.085 s bridge; local collision/query readiness is reported separately; route candidate survives final composition |
-| M3 — FloatingIslands volumetric proof | 2 rounds | Walkable island cluster with underside/cliff views, water/body overlay, tile/LOD seam views and bound counters | Stable field/feature IDs; no false interval proof; route support is visible and capsule-swept |
+| M3 — FloatingIslands volumetric proof and Unreal delivery | 3 rounds | Walkable island cluster with underside/cliff views, tile/LOD seam views, imported manifest, BuildHost proof and cooked route collision | Stable field/feature IDs; no false interval proof; route support is visible and capsule-swept |
 | M4 — route, edit and water law | 2 rounds | Owner can inspect before/after edit views and traverse the tested route; report shows protect-or-replace transaction and unchanged seasonal water IDs | Final-field capsule clearance/support passes; edit either preserves route or atomically installs a replacement; water remains fixed |
 
 M1 goes first because the owner needs to judge crisp geometry before a slow legacy/native comparison