feat(descent): landing ROOMS and a walkable tunnel -- per Jahni's correction

Jahni corrected the design: "the connection between level is a tiny tunnel
connecting both strate, not vertical, it needs to be walkable" and "'the
spine' shouldn't be carved except optionally from the top first strate,
then it's used to have a landing room".

COMPOSER-NOTES §6.8 had said the spine "provides a clean landing space, not
a continuous open shaft" -- and the implementation carved a vertical
cylinder anyway. A vertical cylinder has no walkable floor except at its
bottom, so a carve guaranteeing open AIR guaranteed nothing STANDABLE.
That one omission is behind five of my dead hypotheses this week.

Now:
  origin spine   a finite rounded ROOM per strate, no vertical bore.
                 radius 14 -> 8 m wide, 7.5 m tall
  descent        a walkable tunnel, single-file by design: 3 m mouth,
                 2.5 m waist, gradient capped at a NAMED 15 deg
  exotic styles  VerticalShaft / SpiralDescent / CascadingDrops /
                 CrackCrevice preserved, no longer the default

⚠️ THE GEOMETRY BITES, and it is worth Jahni's eye: at 15 deg a 32 m drop
needs 119.4 m of horizontal run -- about 59.7 m per switchback leg. That is
a long walk between strates. It is the honest consequence of "walkable",
not a tuning artifact, and the alternative is a steeper number.

⭐ AND THE ROOT CAUSE GOT NAMED A THIRD TIME, by Codex mid-run: "the round
tube was hollow air but had no authored support strip, so 'open' still did
not mean 'standable'." Tunnels now carry a floor band, and the root join
terminates in the finite origin room rather than an annular shaft hub.

Measured, commandlet sweep, 8 archetypes x 8 seeds, 64/64 valid:
  origin column has player-fit cells   17/64 -> 63/64
  origin column reachable               0/64 ->  7/64
  arrival landing probes            315/320 fit AND in the arrival component
  tunnel audit    5,916/5,916 floor and capsule samples pass; zero gradient,
                  floor, capsule, geometry or seal failures
  narrow-gap events 0        box verdicts 14 checked, 0 violations

⚠️ arrival->departure is 6/64. The landings and tunnels are now provably
walkable; what remains is the INTRA-STRATE vertical connectivity problem
found in 6b91669 -- floors at different levels inside a strate with nothing
joining them. Separate and larger. Not tuned toward.

⚠️ PROCESS: this took 5.7 hours, of which Codex used 4 SECONDS of CPU. The
rest was polling the 73-minute automation suite at ~10% machine load. The
commandlet exists to avoid exactly that. New rule recorded: iterate with the
commandlet, full suite ONCE at the end.

Editor + Shipping builds clean. Automation 32/32, 0 failed.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_012aheo2crrZmHuYtPpdY2Cb

Source/VoxelForge/Private/VoxelStrateMeasure.cpp

@@ -2863,7 +2863,8 @@ bool VF_MeasurePlayerFitWalkWithSampler(
     const FVector& AVoxel,
     const FVector& BVoxel,
     const FVoxelStrateMeasureSettings& Settings,
-    FVoxelPlayerFitWalkReport& OutReport)
+    FVoxelPlayerFitWalkReport& OutReport,
+    const TArray<FVector>* ComponentProbePoints)
 {
     using namespace VoxelStrateMeasurePrivate;
 
@@ -3038,6 +3039,28 @@ bool VF_MeasurePlayerFitWalkWithSampler(
         ? Components[Start] : INDEX_NONE;
     const int32 GoalComponent = Goal >= 0 && Components.IsValidIndex(Goal)
         ? Components[Goal] : INDEX_NONE;
+
+    if (ComponentProbePoints != nullptr)
+    {
+        OutReport.ComponentProbePlayerFit.Init(0u, ComponentProbePoints->Num());
+        OutReport.ComponentProbeInStartComponent.Init(0u, ComponentProbePoints->Num());
+        for (int32 ProbeIndex = 0; ProbeIndex < ComponentProbePoints->Num(); ++ProbeIndex)
+        {
+            int32 ProbeCell = INDEX_NONE;
+            const FVector& ProbePoint = (*ComponentProbePoints)[ProbeIndex];
+            if (!FindCellForPoint(Grid, ProbePoint, ProbeCell)
+                || !IsEligiblePlayerFitCell(Grid, PlayerFitMask, ProbeCell))
+            {
+                continue;
+            }
+            OutReport.ComponentProbePlayerFit[ProbeIndex] = 1u;
+            if (StartComponent >= 0 && Components.IsValidIndex(ProbeCell)
+                && Components[ProbeCell] == StartComponent)
+            {
+                OutReport.ComponentProbeInStartComponent[ProbeIndex] = 1u;
+            }
+        }
+    }
     if (StartComponent >= 0)
     {
         float BestOriginDistanceSquared = FLT_MAX;