Add connected cave biomes and lighting

.github/workflows/tests.yml

@@ -70,6 +70,7 @@ jobs:
             tools/player_target_verify.tscn \
             tools/worldgen_cactus_verify.gd \
             tools/worldgen_tree_verify.gd \
+            tools/worldgen_cave_verify.gd \
             tools/frame_pacing_verify.gd
 
       - name: Upload check logs

ROADMAP.md

@@ -150,15 +150,15 @@ Current state: the TerraForged-inspired staged pipeline is live under `world/wor
 - [ ] Structures / POIs — deterministic, seam-safe ruins, abandoned camps, mineshafts, and watchtowers placed from global anchors. Must respect player edits and regenerate consistently across chunks; loot and inventory hooks stay with the gameplay pass
 
 ### Caves and underground
-- [x] Phase 1 — wormhole tunnels: connected cell-anchored tunnel segments and sparse seam-safe diagonal surface entrances replace the old per-voxel threshold caves.
-- [x] Phase 2 — large caverns: cell-anchored varied caverns and rare mega-caves, lava lakes, aquifers, damp floor patches, and ceiling/floor stone formations.
+- [x] Phase 1 — endless hybrid cave network: Minecraft/Luanti-inspired absolute-coordinate spaghetti and cheese density fields provide organic seam-free tunnels/chambers, while a five-depth-band deterministic 48-block graph guarantees that every canonical trunk continues indefinitely. Curved trunks, cross-links, mandatory vertical connectors, and node chambers replace the isolated 2-4-segment worms; surface entrances now join graph nodes instead of ending blindly in stone.
+- [x] Phase 2 — large caverns: graph-attached chambers, cell-anchored varied caverns and rare mega-caves, lava lakes, aquifers, damp floor patches, and ceiling/floor stone formations.
 - [x] Phase 3 — underground features: damp mud/mycelium cave patches, depth-banded ore veins, aquifers, lava pockets, and stone formations. Random deep cobblestone variation was removed so cobblestone remains player-made; mineshafts/ruins remain separate future structure work.
-- [ ] Cave-aware lighting and meshing — verify sky-light flood fill around large openings, that caves stay dark, and that `ChunkMesher` light-volume bounds hold for big caverns.
-- [ ] Cave dressing — stalactites/stalagmites, dripstone columns, moss, and small underground pools so cave interiors are not bare stone
-- [ ] Cave biomes — lush and deep-dark variants with distinct ambience, vegetation, and materials layered onto `world/worldgen/biome_catalog.gd`
-- [ ] Geodes and crystal formations — rare hollow geodes and mineral deposits so deep exploration has landmarks beyond ore veins
+- [x] Cave-aware lighting and meshing — `ChunkMesher.build_light_volume()` exposes the temporary 3x3 volume to deterministic fixtures; missing chunks are closed light boundaries rather than daylight leaks, water/leaf side seeds use their real attenuation, flood queues grow instead of silently truncating, and edits/commits invalidate all eight sampled neighbors (including pending-job races). `tools/worldgen_cave_verify.gd` pins sealed darkness, a large opening's finite falloff, colored crystal light, and exact cavern-volume bounds
+- [x] Cave dressing — the sparse global cave lattice now finds nearby floors/ceilings and places paired dripstone, short columns, damp moss/mycelium, hanging cave growth, sculk/deepstone patches, and small floor-supported pools without returning to a full 3D voxel scan
+- [x] Cave biomes — `BiomeCatalog` appends `LUSH_CAVES`/`DEEP_DARK` as a separate coherent 3D region layer (surface IDs stay stable); exposed cave materials and vegetation follow that layer, while `VoxelWorld.get_cave_ambience()` scans to the loaded column top so even tall mega-caves receive distinct green/teal fog and light floors. Cave regions cover most underground territory, and the HUD replaces the surface-biome label while one is active
+- [x] Geodes and crystal formations — rare global-cell spheres clip seam-safely across chunks with a dark shell, calcite lining, hollow core, amethyst deposits, and emissive crystal buds that automatically seed the RGB block-light flood
 - [x] Ore distribution overhaul — deterministic cell-anchored coal, iron, and gold vein segments use depth bands and replace stone after caves are carved.
-- [x] Cave performance guardrails — cell-anchored carving replaces full-height 3D cave scans; clipped ellipsoids hoist column limits, aquifer decisions are chunk-local, and normal full generation averages ~40 ms in the pinned CLI benchmark.
+- [x] Cave performance guardrails — noise carving scans only eligible stone below each column's protected surface and Y100 cap; graph/cavern stamps clip to the target chunk from bounded owner halos; aquifer decisions remain chunk-local. The richer network raises pinned normal full generation from ~44 ms to ~58 ms while compact LOD remains ~16 ms. The cave verifier follows 128 trunk cells and flood-fills a 5x5 independently generated hybrid fixture: 6.9% air with a 32,128-block component spanning the full 80x92x80 volume.
 
 ### Verification
 - [x] Tree integrity / groves / cactus closure — fuller connected broadleaf crowns cover limb ends; immutable tree-site decisions and overlap regressions prevent chunk-owner/canopy disagreements. Forest, taiga, and jungle use a dedicated deterministic grove field with denser patches and clearings while respecting density controls. Cactus placeholder margins are cropped in runtime texture preparation to close cube edges/caps; opacity and stacked-mesh tests pass. Forward+ grove and cactus captures inspected.

assets/placeholders/caves/README.md

@@ -0,0 +1,6 @@
+# Cave placeholder textures
+
+These 64 px cave-biome, geode, and crystal textures were generated specifically
+for RedotCraft. They do not contain third-party artwork. Regenerate them with:
+
+`redot --headless --path . --script res://tools/gen_underwater_textures.gd`

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