planner: four-strate owner plan spawns (L66); pinned 2-strate regression fixture

- Core caps each passage mouth reach to its own strate's usable content band (owner
  DA_Strate1 exports ReachMax=5000 owner voxels, which put the SW->FI lower mouth 79.5 m
  below FI, inside TN).
- Unreal adapter: SW route search keeps the old 64 m candidates first, then a bounded
  single-mouth search with shorter lengths; logs candidate/rejection counts.
- Internal-chain passage floor/support tweaks (only with >2 strates): ripple 1-2 4.78->2.90 cm,
  2-3 3.57->0.10 cm. Interfaces still 0/3 walkable (59/3/2 unsupported).
- verify.py: legacy tiers use Standalone/data/regression/owner_world_2strate_l61.json; new
  four-strate stage reads its expectations from owner_world.json (currently red on interfaces).
- Unreal trace L14 vs HEAD, same assets (16-chunk FlatPlain): 12.20 vs 12.56 worker-s; no x2.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_016dhxM43dnWvUu2B5Ph1iG1

Standalone/Core/src/ResolvedLayoutInternal.h

@@ -2325,8 +2325,22 @@ bool PlanResolvedLayoutPassagesV1(ResolvedLayoutSnapshotV3& layout,std::int32_t
         const std::int64_t midRadius=std::max<std::int64_t>(
             static_cast<std::int64_t>(std::llround((upperIsSurfaceWorld?3.5:1.5)*qPerMetre)),
             cfg?cfg->midRadiusSubvoxels:mouthRadius);
-        const std::int64_t reachMinimum=cfg?std::max<std::int64_t>(0,cfg->reachMinimumSubvoxels):8*qPerMetre;
-        const std::int64_t reachMaximum=cfg?std::max<std::int64_t>(reachMinimum,cfg->reachMaximumSubvoxels):24*qPerMetre;
+        const std::int64_t requestedReachMinimum=cfg
+            ?std::max<std::int64_t>(0,cfg->reachMinimumSubvoxels):8*qPerMetre;
+        const std::int64_t requestedReachMaximum=cfg
+            ?std::max<std::int64_t>(requestedReachMinimum,cfg->reachMaximumSubvoxels):24*qPerMetre;
+        // Keep the landing several metres inside the stratum's authored content.
+        // Near a band edge, the sampled native terrain can exist at the centerline
+        // while the full capsule footprint has no supporting ground.
+        const std::int64_t mouthClearance=std::max(mouthRadius,midRadius)+2*qPerMetre;
+        const auto usableReach=[&](const ResolvedLayoutStratumV2& stratum)
+        {
+            const std::int64_t depth=contentZQ(stratum.content.topMicrometres)
+                -contentZQ(stratum.content.bottomMicrometres);
+            return std::max<std::int64_t>(0,depth-mouthClearance);
+        };
+        const std::int64_t upperReachLimit=usableReach(upper);
+        const std::int64_t lowerReachLimit=usableReach(lower);
         const std::uint32_t style=cfg?std::min<std::uint32_t>(cfg->style,3u):1u;
         const std::uint32_t segments=cfg?std::clamp<std::uint32_t>(cfg->segments,16u,48u):20u;
         const std::int64_t wander=cfg?std::max<std::int64_t>(0,cfg->wanderSubvoxels):3*qPerMetre;
@@ -2362,16 +2376,30 @@ bool PlanResolvedLayoutPassagesV1(ResolvedLayoutSnapshotV3& layout,std::int32_t
                 if(!hasUpperRoute)
                 {
                     upperMouth[0]=xy[0];upperMouth[1]=xy[1];
-                    const auto reach=reachValue(PassageSeed(seed,upper.strateIndex,lower.strateIndex,
-                        connection,0x55505248u),reachMinimum,reachMaximum);
+                    const auto requestedReach=reachValue(PassageSeed(seed,upper.strateIndex,
+                        lower.strateIndex,connection,0x55505248u),
+                        requestedReachMinimum,requestedReachMaximum);
+                    const auto reach=std::min(requestedReach,upperReachLimit);
                     upperMouth[2]=contentZQ(upper.content.bottomMicrometres)+reach;
+                    if(requestedReach>upperReachLimit)
+                        std::printf("[ResolvedPassageReachClamp] id=%s side=upper sampled_m=%.3f usable_max_m=%.3f selected_m=%.3f status=CLAMPED\n",
+                            passage.stableId.c_str(),requestedReach/static_cast<double>(qPerMetre),
+                            upperReachLimit/static_cast<double>(qPerMetre),
+                            reach/static_cast<double>(qPerMetre));
                 }
                 if(!hasLowerRoute)
                 {
                     lowerMouth[0]=xy[0];lowerMouth[1]=xy[1];
-                    const auto reach=reachValue(PassageSeed(seed,upper.strateIndex,lower.strateIndex,
-                        connection,0x4c4f5752u),reachMinimum,reachMaximum);
+                    const auto requestedReach=reachValue(PassageSeed(seed,upper.strateIndex,
+                        lower.strateIndex,connection,0x4c4f5752u),
+                        requestedReachMinimum,requestedReachMaximum);
+                    const auto reach=std::min(requestedReach,lowerReachLimit);
                     lowerMouth[2]=contentZQ(lower.content.topMicrometres)-reach;
+                    if(requestedReach>lowerReachLimit)
+                        std::printf("[ResolvedPassageReachClamp] id=%s side=lower sampled_m=%.3f usable_max_m=%.3f selected_m=%.3f status=CLAMPED\n",
+                            passage.stableId.c_str(),requestedReach/static_cast<double>(qPerMetre),
+                            lowerReachLimit/static_cast<double>(qPerMetre),
+                            reach/static_cast<double>(qPerMetre));
                 }
             }
             if(!radialWithin(upperMouth,placementRadius)||!radialWithin(lowerMouth,placementRadius))