docs: Q3 tick the stale PENDING BUILD markers + CODEMAP rows for the new symbols

Q3: fable-idea F20 phases 1/2 and F18, REVIEW_FINDINGS perf pass 2 and batch 3,
and ARCHITECTURE's biome full-param redesign were all still carrying
"CODE-COMPLETE, PENDING BUILD" markers dated 07-04/-06/-08. Jahni confirmed on
2026-07-26 that everything is built and working (AUDIT-2026-07.md §0), so the
documents were misreporting project state. Ticked with the date they were
ticked, not just the date they were built.

Deliberately NOT ticked: ARCHITECTURE's F6 master material graph. Its C++ half
is built, but the material graph itself is editor-side work that is genuinely
still open, and ticking it would recreate the problem this queue item fixes.

CODEMAP discipline for this batch: new §3.2b (the VoxelDensityOp contract), new
§3.12 (Private/Tests), the EVoxelTileClass move into §3.2, and
FChunkBiomeCache::Invalidate under the biome types row.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

ARCHITECTURE.md

@@ -625,7 +625,7 @@ change *anything*, e.g. frequencies, which scalar multipliers couldn't.)
 - **Preview tool.** `AVoxelWorld::BakeBiomePreview()` (CallInEditor) bakes biome / relief / moisture
   to `Saved/BiomePreview.png` via a transient generator (no PIE). Needs the `ImageWrapper` module.
 - **Status:** A (field+asset+preview), B (terrain), C (content/atmosphere) verified in-editor.
-  Full-param redesign (surface output-blend) code-complete, pending build. Cave structural biomes
+  Full-param redesign (surface output-blend) ✅ BUILT & WORKING (ticked 2026-07-27). Cave structural biomes
   deferred (determinism, see above). Per-voxel biome warp (+2 Perlin) & content `GetDominantBiomeAt`
   are future T1.a column-cache candidates.
 
@@ -657,7 +657,8 @@ generic biome field), not just SurfaceWorld. Empty `Biomes[]` ⇒ all-zero colou
 - **Perf.** Free where a strate has no biomes (`GetBiomeMaterialAt` early-outs to palette 0). Otherwise
   one biome resolve per unique vertex, bounded by the per-chunk biome cache (don't feed it a chunk key —
   keep the box validity, §8.10). Coarse far tiles have few vertices.
-- **Status:** C++ code-complete, pending in-editor build + the master material graph (editor-side work).
+- **Status:** C++ ✅ BUILT & WORKING (ticked 2026-07-27). The master material graph is still
+  editor-side work and is deliberately NOT ticked — that half is Jahni's, not the code's.
 
 ## 9. Multiplayer model (listen-server first, dedicated-friendly)