feat(strate): the layout is a set, not a sequence -- and the suite is green

Tier 0. Reordering Settings->StratePool in the editor used to change every
world in the game, because Initialize Fisher-Yates shuffled the array in
editor order. The pool is now sorted by stable soft-asset path before the
shuffle, so the layout is a pure function of (seed, pool contents as a SET).
The selection algorithm itself is untouched -- same Fisher-Yates, same cycling,
same FixedStrates handling, same Z ranges. Sorting by pointer would have looked
right and been load-order dependent, which is the trap here.

GeneratePassages walked one sequential FRandomStream across every strate, so
changing an early connection count shifted every later passage. Each draw is
now a salted VoxelHash of (seed, boundary index, connection index), with the
distributions preserved exactly -- ToFloat01 returns [0,1), so Lerp(Min,Max,t)
reproduces FRandRange precisely.

Codex implemented it and caught a real flaw in my spec: I asked for a test that
permutes the pool and asserts the passages match, but once the layout is
order-independent that test cannot fail whether or not the passage fix works --
the layout comes out identical, so even the old sequential stream would agree.
It added the perturbation that actually bites: change an early connection count
and verify every later boundary keeps its own values. It also contradicted me
on passage type being randomly drawn. It isn't, and it preserved that.

Built VoxelMEditor clean, then ran the suite headless: 16 succeeded, 0 failed,
0 not run. That also closes the thread OPSTACK-HANDOFF.md left open -- 4d33321
and 91585ea were built but never re-verified, and both acceptance conditions
are now met: violations 0 everywhere (12 of 40 TunnelNetwork tiles proved over
15972 brute-forced voxels), all equivalences green. No revert needed.

Expected: every seed now lays out differently than before. Accepted,
pre-content-lock.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01DPUuCtn5zTLui6WybLbkNb

COMPOSER-NOTES.md

@@ -345,11 +345,12 @@ needs a guard, or the caves vanish with no error.
 
 ### ⚠️ 6.4 The primordial law has a real hole TODAY
 
-`UVoxelStrateManager::GeneratePassages` places every inter-strate passage as: `FRandomStream(CachedSeed
-^ 0x50A55A6E)` → random angle around the (0,0) spine → random distance in the config range → random
-reach into each strate. **Nothing consults the destination strate's cave layout.** Carving is a
-structural-post invariant so the tube *is* air — but whether its lower mouth joins the lower strate's
-connected space is pure luck. **A player can descend a passage and arrive in a sealed pocket.**
+`UVoxelStrateManager::GeneratePassages` places every inter-strate passage as independently salted
+hashes of `(seed, upper-strate index, connection index)` → random angle around the (0,0) spine →
+random distance in the config range → random reach into each strate. **Nothing consults the
+destination strate's cave layout.** Carving is a structural-post invariant so the tube *is* air — but
+whether its lower mouth joins the lower strate's connected space is pure luck. **A player can descend
+a passage and arrive in a sealed pocket.**
 
 **Fix — make the strate OFFER a landing site, don't let the passage gamble.** Add to the field-source
 contract something like `SuggestOpenPoint(WorldX, WorldY) -> optional Z`. Every source already knows
@@ -372,16 +373,18 @@ you see the hole); and ⭐ **make the mouth a PLACE, not a hole** — the `Sugge
 lands the passage in a room, so make that room distinctive. Cracks in walls are forgettable; rooms are
 landmarks, and that is what makes it findable on the *second* visit, which quests need.
 
-### ⚠️ 6.6 The layout depends on the pool's CONTENTS *and its ORDER*
+### ✅ 6.6 The layout depends on the pool's CONTENTS, not its ORDER (BUILT + TESTS GREEN)
 
-`Initialize` Fisher-Yates shuffles `Settings->StratePool` with `FRandomStream(WorldSeed)`, then cycles it
-(`PoolCursor % Num`) when `TotalStrates` exceeds the pool. So **reordering the pool asset in the editor
-changes every world**, and a pool smaller than the strate count repeats entries in a fixed order.
+Before Tier 0, `Initialize` Fisher-Yates shuffled `Settings->StratePool` in editor order with
+`FRandomStream(WorldSeed)`, then cycled it (`PoolCursor % Num`) when `TotalStrates` exceeded the pool.
+So **reordering the pool asset in the editor changed every world**, and a pool smaller than the strate
+count repeated entries in a fixed order.
 
-⇒ Use `hash(seed, slotIndex[, attempt])` instead, over a pool sorted by a stable key. The pool becomes a
-**set** rather than a sequence: tidying the asset stops changing worlds, and each slot's roll becomes
-independent of its neighbours'. Adding or removing a strate type still changes worlds — unavoidable, and
-the reason content lands at wipes.
+⇒ **Tier 0 is now implemented:** load the pool, sort it by the stable soft-asset path, then keep the
+existing Fisher-Yates shuffle and cycling algorithm. The pool is a **set** rather than an editor-ordered
+sequence: tidying the asset stops changing worlds. Adding or removing a strate type still changes
+worlds — unavoidable, and the reason content lands at wipes. A per-slot hash would be a different
+sampling algorithm and is intentionally deferred.
 
 ### ⚠️ 6.7 A bounded world needs an XY EDGE SEAL, which does not exist
 
@@ -455,7 +458,7 @@ refactor, where three weeks of correct work produced a world unchanged by a sing
 ### Tier 0 — safety nets, true regardless of the composer
 - ✅ **X-macro guard test** — DONE, green.
 - ✅ **Actor-space sweep** — DONE, confirmed off-origin.
-- **Order-independent placement** (§6.6). *Standalone value:* the strate pool asset can be reordered or
+- ✅ **Order-independent placement** (§6.6) — DONE. Built clean, `VoxelForge.Determinism.LayoutOrderIndependence` green. *Standalone value:* the strate pool asset can be reordered or
   tidied without changing every world. Small and isolated.
 
 ### Tier 1 — the primordial law (a BUG FIX, not composer work)
@@ -525,3 +528,36 @@ Game-design questions live in **[GDD.md](GDD.md) §16**. These are the ones that
 5. **Whether op discovery** (promoting good sub-stacks into named reusable units) is ever worth it.
    Parked: the existing parameter space is already vastly larger than a hundred seasons could explore.
    **The scarce resource is judgment, not vocabulary.**
+
+---
+
+## 10. Verification log
+
+**2026-08-17 — full suite run headless, first time this session.** Built `VoxelMEditor Win64
+Development` clean (no errors, no warnings), then:
+
+```
+UnrealEditor-Cmd.exe VoxelM.uproject -ExecCmds="Automation RunTests VoxelForge;Quit"
+                     -unattended -nopause -nosplash -NullRHI -ReportExportPath=...
+```
+
+**Result: 16 succeeded, 0 failed, 0 not run, 0 succeeded-with-warnings.** 25.7 s.
+
+Tests: BoxVerdictFold · ClassifyTileSoundness (×2) · CrossPlatformDigest · DensityPurity ·
+DiffLayerContention · FloatingIslandEquivalence · LargeSeedSurvives · **LayoutOrderIndependence** ·
+LiveEditInvalidation · MazeEquivalence · SlabEquivalence · **StrateParamBlendCoverage** ·
+SurfaceHeightEquivalence · TunnelNetworkSpineEquivalence · VerticalShaftEquivalence.
+
+**⭐ This closes the pending-verification thread opened by `OPSTACK-HANDOFF.md`.** That file flagged
+commits `4d33321` (Sol's boundary fold) and `91585ea` as *built but NOT re-verified*, with two
+acceptance conditions. Both now met:
+- **`violations` = 0** everywhere. Measured: TunnelNetwork at production defaults **12 of 40 tiles
+  proved AllSolid, 15 972 voxels brute-forced, 0 violations**; VerticalShafts **32 of 60 proved, 0
+  violations**; dense fixture 0 proved / 40 Mixed, 0 violations.
+- **All equivalence tests green** — Maze, Slab, TunnelNetworkSpine, VerticalShaft, FloatingIsland,
+  SurfaceHeight.
+
+⇒ **No revert of `4d33321` is needed.** The 39 % tile-skip win stands, verified rather than assumed.
+
+⚠️ **Read the PROVED counts as measurements, never as contracts.** What is asserted is that none of
+them is *wrong* — a false verdict leaves no geometry and no collision behind it.