chore(repo): archive historical docs under Docs/archive, drop tracked pycache

Move closed audits, task briefs, design rounds, perf reports, the OPSTACK
plan/progress logs and WORK-NEXT.md into Docs/archive/ (git mv, history kept).
Whitelist Docs/ in the strict .gitignore, ignore Tools/**/__pycache__/, and
remove the tracked .pyc. Repoint references in the kept docs and in non-test
source comments to the new paths.

.gitignore

@@ -12,8 +12,13 @@
 # The guarded single-entry test harness is source, not generated output.
 !/Tools/
 !/Tools/**
+/Tools/**/__pycache__/
+
+# Closed / historical documents.
+!/Docs/
+!/Docs/**
 
 !VoxelForge.uplugin
 
-# Keep every design / doc markdown at any depth (AUDIT P1 — these were untracked)
+# Keep every design / doc markdown at any depth
 !*.md

ARCHITECTURE.md

@@ -130,7 +130,7 @@ in §10.
 ⚠️ **The `switch` above is no longer the only density path.** All 8 archetypes also exist as
 **operator stacks**, selected per strate by
 `bUseOperatorStack` and evaluated instead of the `switch`; each is bit-identical to the function in
-its row. The design lives in `OPSTACK-PLAN.md` / `OPSTACK-DECOMPOSITION.md`, the symbol index in
+its row. The design lives in `Docs/archive/OPSTACK-PLAN.md` / `Docs/archive/OPSTACK-DECOMPOSITION.md`, the symbol index in
 `CODEMAP §3.2d` — not repeated here. What matters for *this* document: the archetype table describes
 what the world IS, and both paths compute it.
 
@@ -521,7 +521,7 @@ flat floor. **There is no connector to the origin landing room at `(0,0)`.** The
 those radial roads after a playtest (`d97373c`, 2026-09-08: they cut straight through everything);
 room joins are flattened to walkable height instead. A source-fit landing therefore stays local to
 the room it was fitted into (`GeneratePassages`, the `VF_BuildPassageLanding` calls).
-⚠️ Open gap (Sol's code review, `DESIGN-SOL-2026-09-15-CODE.md` §1.3/§2.4): when the footing query
+⚠️ Open gap (Sol's code review, `Docs/archive/DESIGN-SOL-2026-09-15-CODE.md` §1.3/§2.4): when the footing query
 declines, the landing falls back to the historical random reach, and nothing proves that pose joins
 the walk network. The canonical capability gate covers one scenario, not every seed or mix.
 Proposed fix, not built: retry deterministically at other candidate spots instead of falling back.
@@ -833,7 +833,7 @@ driven by `EditorBrush*` props.
   = 0; `=1` restores it as an A/B instrument). Measured on the headless game path with nested
   refinement off, the classifier plus its exact validation cost more than they saved. Mode 0 had
   ready p95 182 vs 190-195 ms, generation p95 125-127 vs 139-141 ms, and 18% fewer density calls,
-  with 841/841 tiles triangle-identical (WORK-NEXT.md). Proving a 33³ core uniform costs almost
+  with 841/841 tiles triangle-identical (Docs/archive/WORK-NEXT.md). Proving a 33³ core uniform costs almost
   as much as meshing 35³. The history below explains why it existed. Its soundness tests still
   guard it.
 - **Trivial-empty tile reject (T1.d) — v2 SHIPPED (2026-07-05); v1 was reverted 2026-06-26.**

CODEMAP.md

@@ -138,7 +138,7 @@ remains `0`, and lateral regions remain gated off.
 ### 3.2b Density operator stack contract — `Public/VoxelDensityOp.h` (plain C++, no UHT)
 **Production path behind a per-strate opt-in** — the stack is built/evaluated by `GetDensityAt` for
 all eight archetypes when `bUseOperatorStack` is enabled, while the legacy `switch` remains the
-reference path for opt-out strates. See [OPSTACK-PLAN.md](OPSTACK-PLAN.md) for the decomposition.
+reference path for opt-out strates. See [Docs/archive/OPSTACK-PLAN.md](Docs/archive/OPSTACK-PLAN.md) for the decomposition.
 
 | Symbol | Notes |
 |--------|-------|
@@ -711,7 +711,7 @@ Bourke). Cube corner/edge layout documented at top (lines 7-37). Rarely needs ed
 ---
 
 ### 3.12 Automation tests — `Private/Tests/` (added 2026-07-27, `#if WITH_DEV_AUTOMATION_TESTS`)
-The plugin's first tests (`OPSTACK-PLAN.md` Phase 0.5). Run them from the editor's
+The plugin's first tests (`Docs/archive/OPSTACK-PLAN.md` Phase 0.5). Run them from the editor's
 **Session Frontend → Automation**, filter `VoxelForge`.
 
 | File | Test name | What it proves |

COMPOSER-NOTES.md

@@ -36,7 +36,7 @@ composer fills in; nobody opens it in the editor any more.
 
 ### This is op-stack "Phase 3", and it is REOPENED
 
-The 2026-08-16 `OPSTACK-HANDOFF.md` says in bold *"Do not start Phase 3."* **That is superseded.**
+The 2026-08-16 `Docs/archive/OPSTACK-HANDOFF.md` says in bold *"Do not start Phase 3."* **That is superseded.**
 Asked what the world was missing, Jahni described exactly Phase 3 plus a composer above it.
 
 It is **not** a restart of the refactor. The eight operators are live, composable, and production. What
@@ -1490,7 +1490,7 @@ roughness and should stay late in the stack.
 
 Kept because each cost real time or would otherwise be repeated.
 
-- ⛔ **"Do not start Phase 3" is SUPERSEDED.** `OPSTACK-HANDOFF.md` still says it; believe this file.
+- ⛔ **"Do not start Phase 3" is SUPERSEDED.** `Docs/archive/OPSTACK-HANDOFF.md` still says it; believe this file.
 - ⛔ **Jahni does not want to author strates either.** The composer must invent them. An earlier reading
   had him authoring strates while the system arranged them — one level too shallow, and it shaped a
   whole afternoon of wrong design.
@@ -1553,7 +1553,7 @@ build succeeded (14 actions). The full headless suite reported **22 succeeded, 0
 determinism, box-verdict, and connectivity checks stayed green. The 4b→4h fuse was deliberately
 not applied after the intervening-channel audit above.
 
-**⭐ This closes the pending-verification thread opened by `OPSTACK-HANDOFF.md`.** That file flagged
+**⭐ This closes the pending-verification thread opened by `Docs/archive/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

Source/VoxelForge/Public/VoxelDensityOp.h

@@ -1,6 +1,6 @@
 // VoxelDensityOp.h
 // LE CONTRAT de la pile d'opérateurs de densité / THE density operator stack CONTRACT.
-// Phase 1 de OPSTACK-PLAN.md. The contract is implemented by the opt-in stack path in
+// Phase 1 de Docs/archive/OPSTACK-PLAN.md. The contract is implemented by the opt-in stack path in
 // UVoxelGenerator::GetDensityAt; the legacy archetype switch remains for non-opt-in strates.
 //
 // ─────────────────────────────────────────────────────────────────────────────────────────

Source/VoxelForge/Public/VoxelStrateDefinition.h

@@ -128,7 +128,7 @@ public:
      *
      * ⚠️ Do NOT flip this on a strate mid-session and expect the old and new geometry to agree to
      * the bit — they differ by ~1-2 ULP with ZERO isosurface crossings, so the shape is identical
-     * but the floats are not (`AUDIT-2026-07.md §C10`). Regenerate the world after changing it
+     * but the floats are not (`Docs/archive/AUDIT-2026-07.md §C10`). Regenerate the world after changing it
      * rather than letting old and new tiles sit side by side.
      *
      * Pile d'opérateurs (expérimental) : génère cette strate via la pile composable au lieu du

Source/VoxelForge/VoxelForge.Build.cs

@@ -26,7 +26,7 @@ public class VoxelForge : ModuleRules
 		//
 		// Precise resolves to "/fp:precise" on MSVC and "-ffp-contract=off" on Clang — both
 		// IEEE-754 compliant with no FMA contraction, so the two toolchains agree BY CONSTRUCTION
-		// rather than by luck. That is the fix for AUDIT-2026-07.md C9.
+		// rather than by luck. That is the fix for Docs/archive/AUDIT-2026-07.md C9.
 		//
 		// COST: /fp:precise forbids the reassociation and contraction /fp:fast allowed, on a
 		// noise-heavy hot path. Expect a measurable perf regression and check it against

fable-idea.md

@@ -46,7 +46,7 @@ So: normals can cost as much as the entire density grid; a SurfaceWorld chunk do
 
 **T1.d — Chunk classification: skip trivially solid/air chunks before sampling.** ✅ DONE 2026-07-05
 ⛔ **Turned OFF in streaming 2026-09-13.** After the operator stack, it cost more than it saved on the
-game path (WORK-NEXT.md A/B). Do not re-propose tile classification without a design that is
+game path (Docs/archive/WORK-NEXT.md A/B). Do not re-propose tile classification without a design that is
 cheaper than meshing the tile.
 (v2 — `UVoxelGenerator::ClassifyTile`, see ARCHITECTURE §8.10; a 2026-06-26 v1 with a global ceiling
 bound was reverted for roof holes. Trigger: trace showed 84 % of GenerateMesh calls produced empty
@@ -214,7 +214,7 @@ fade with slope ⇒ seamless at biome borders; placement hashes are pure `(seed,
 "ops finally work on the surface" win; **(2)** overhang (3D band, slope-conditioned); **(3)** spike/hole (placed +
 shortlist + ClassifyTile guard) — most cost, do last.
 
-**PHASE 1 — ✅ BUILT & WORKING** (built 2026-07-08; marker ticked 2026-07-27 — confirmed working by Jahni 2026-07-26, see `AUDIT-2026-07.md §0`). Heightfield ops shipped: **Cliff** (slope-gated STEEPENING —
+**PHASE 1 — ✅ BUILT & WORKING** (built 2026-07-08; marker ticked 2026-07-27 — confirmed working by Jahni 2026-07-26, see `Docs/archive/AUDIT-2026-07.md §0`). Heightfield ops shipped: **Cliff** (slope-gated STEEPENING —
 push height from the local mean where steep ⇒ sheer walls; the slope-conditioned one, hugs steep terrain;
 v1 band-snap was too subtle, reformulated to steepening after Jahni's "doesn't change much"), **Terrace** (relief-gated plateau quantize, now with
 `TerraceHardness` soft-round↔crisp-mesa), **LayerLines** (sedimentary sine shelves, slope-expressed). *Design
@@ -231,7 +231,7 @@ height oracle `ComputeSurfaceTerrainZ` (new `SampleSurfaceStructuralZ` helper =
 an XY offset for Cliff's slope) so MC/sheets/ClassifyTile/deco/BP-bridge all agree, no T1.d interference. Revisit
 the array+condition model for **phase 2 (overhangs)** where per-entry slope-gating earns its keep.
 
-**PHASE 2 — ✅ BUILT & WORKING** (built 2026-07-08; marker ticked 2026-07-27 — confirmed working by Jahni 2026-07-26, see `AUDIT-2026-07.md §0`). Overhang (first VOLUMETRIC op) as
+**PHASE 2 — ✅ BUILT & WORKING** (built 2026-07-08; marker ticked 2026-07-27 — confirmed working by Jahni 2026-07-26, see `Docs/archive/AUDIT-2026-07.md §0`). Overhang (first VOLUMETRIC op) as
 `FSurfaceGenerationParams` fields (`OverhangStrength/Reach/Height/Frequency/ZScale/SlopeThreshold`, default
 off). **Design NOTE — v1 additive-noise-band was WRONG (Jahni: "does nothing" + sketch of a real cliff lip):
 band-additive noise can only bump the surface where it already is, never make rock jut OUT over a void.**