test(measure): the VerticalShafts disconnection is real, not a coarse lie

Our guard was one-directional. FullResolutionPathIsAir catches the false
POSITIVE -- coarse says joined, reality says walled -- which is the
dangerous direction for safety, so we built it first. The opposite error
was unguarded: a corridor narrower than SampleStep falls between sample
points and vanishes, so connected regions read as separate. That is
exactly what a network of narrow vertical shafts would fake at step 4.

Refinement sweep, radius held constant for the controls:

  step 4 / r256  NOT_CONNECTED  57 comp  largest .119     458,752 cells
  step 4 / r192  NOT_CONNECTED  32 comp  largest .220     258,048
  step 2 / r192  NOT_CONNECTED  27 comp  largest .220   2,064,384
  step 4 / r128  NOT_CONNECTED  20 comp  largest .291     114,688
  step 1 / r128  NOT_CONNECTED  11 comp  largest .303   7,340,032

Both fixed-radius pairs stayed negative, so neither the step nor the
radius explains it. At one-voxel sampling the arrival and departure
mouths are still in different air components.

VerticalShafts is a live primordial-law violation: a player descends into
it and cannot reach its exit.

NotConnected is renamed NotConnectedAtThisResolution and documents its own
limit at the declaration, so a bare negative can never again be read as
proof. CoarseLied names one direction; this names the other.

Sweep split into VoxelForge.Generation.StrateConnectivityRefinement so the
fast test stays fast. 4.4 s. The MaxCells refusal path was exercised and
still refuses.

Build clean, 19 succeeded / 0 warnings / 0 failed.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Bp7FxoQcSoiuhxjuLr6aBM

CODEMAP.md

@@ -312,13 +312,15 @@ representative point, cell count, and count of components holding at least 1% of
 `VF_AreConnected` recovers a deterministic BFS parent path from the same kind of grid and checks
 only that route at full voxel resolution before returning `Connected`. It returns an explicit
 `EVoxelConnectivityResult`; a solid endpoint cell is repaired by snapping to the nearest air cell
-among its 26 neighbours when possible, and reports the snap through its out flags. No UObject state,
-cache, actor, world, or PIE is required.
+among its 26 neighbours when possible, and reports the snap through its out flags. A missing coarse
+route returns `NotConnectedAtThisResolution`: that is evidence only at the grid's resolution,
+because a corridor thinner than `SampleStep` is invisible. No UObject state, cache, actor, world,
+or PIE is required.
 | Symbol | Role |
 |--------|------|
 | `FVoxelStrateMeasureSettings` / `FVoxelStrateMetrics` | Plain settings/result structs for bounded strate sampling and derived measurements; callers may override the interior margin, and results identify the resolved margin/Z window and deterministic component representatives. |
 | `VF_MeasureStrate` | One-grid/one-flood-fill strate metrics; refuses invalid bounds or a grid over `MaxCells`. |
-| `VF_AreConnected` | Coarse 6-connected BFS plus one full-resolution recheck of its recovered route, with explicit endpoint-solid, out-of-window, coarse-lie, and connectivity outcomes. |
+| `VF_AreConnected` | Coarse 6-connected BFS plus one full-resolution recheck of its recovered route, with explicit endpoint-solid, out-of-window, `CoarseLied`, `NotConnectedAtThisResolution`, and connected outcomes. |
 
 ### 3.7 Cave morphology (SDF rooms/tunnels) — `Public/VoxelCaveMorphology.h` + `.cpp`
 Header is rich with inline docs. Two namespaces + a per-chunk cache system.