Add modular holdover fishing world

world/README-WORLD-GRAYBOX.md

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+# NETFISHING holdover world
+
+`world/test_world.tscn` remains the active world. It composes the complete
+temporary map, lighting, paths, bounds, and six region scenes. The practical
+footprint is approximately 180 × 220 world units, including the coastal water
+and outer collision bounds.
+
+## Composition
+
+```text
+TestWorld
+├── Environment
+├── SeabedBoundary
+├── Regions
+│   ├── VillageRegion            (0, 0, 15)
+│   ├── StarterPondRegion       (-42, 0, 15)
+│   ├── RiverRegion               (0, 0, -40)
+│   ├── LakeRegion               (53, 0, -25)
+│   ├── MarshRegion              (56, 0, 38)
+│   └── CoastalDockRegion         (0, 0, -103)
+├── Connectors
+├── Safety
+└── WorldBounds
+```
+
+Every region uses the same ownership groups:
+
+- `Visuals`: replaceable graybox meshes and labels.
+- `StaticCollision`: simple gameplay collision paired with the visuals.
+- `FishingWater`: explicit `FishableWaterRegion` children.
+- `WaterRecovery`: explicit `PlayerWaterTrigger` children.
+- `SafeRespawns`: known-safe `SafeRespawnPoint` markers.
+- `Interactables`: region-owned services, currently used by the village.
+
+`GrayboxRegion` only exposes those explicit child groups plus a stable region
+ID. `TestWorld` is the aggregation boundary; regions do not select fish,
+control recovery, own progression, register globally, or stream themselves.
+
+## Safe editing
+
+Move a whole region by moving its region root under `TestWorld/Regions`. This
+keeps visuals, collision, water, recovery triggers, safe points, and
+interactables synchronized. Moving only a visual mesh does not move collision
+or gameplay volumes, so update its paired collision intentionally when editing
+inside a region.
+
+Safe designer targets:
+
+- Entire region roots under `TestWorld/Regions`
+- Children of `Visuals`, together with paired `StaticCollision`
+- Safe-respawn marker transforms
+- Landmark and label transforms
+- Connector transforms and their complete StaticBody children
+
+Structural land and route blocks extend from the common walkable elevation at
+`y=0` down to approximately `y=-6`. Adjacent blocks meet at deliberate shared
+edges instead of stacking collision surfaces. Decorative plaza/path color is
+non-colliding and sits just above the authoritative ground.
+
+Gameplay-critical children that must stay aligned:
+
+- A water plane, its `FishingWater` Area3D, and its `WaterRecovery` Area3D
+- A dock or bank mesh and its paired shape in `StaticCollision`
+- Safe points and the land/dock they target
+- The Fishing Shop visual root and `FishingShopInteraction`
+
+Rename-sensitive paths:
+
+- `TestWorld/Regions`
+- `VillageRegion/Interactables/FishingShopWorld/FishingShopInteraction`
+- `VillageRegion/Interactables/PelicanCoolerPerch`
+- Each region's `FishingWater`, `WaterRecovery`, and `SafeRespawns` roots,
+  unless its exported NodePaths are updated at the same time
+
+## Adding water and recovery
+
+1. Add a `FishableWaterRegion` Area3D under the region's `FishingWater`.
+2. Give it collision layer 4, a clear location tag, and an explicit fish pool.
+3. Add a matching `PlayerWaterTrigger` under `WaterRecovery`.
+4. Give the trigger collision layer 8, mask 2, matching horizontal coverage,
+   and the correct `surface_height`.
+5. Place two or more safe respawns on nearby broad walkable land.
+6. Validate casting, shoreline collision, recovery entry, and nearest-point
+   selection from every side.
+
+`TestWorld/Safety/BelowWorldFailsafe` is a temporary whole-map recovery net.
+It catches seam and below-world falls that escape normal regional water
+coverage. It supplements rather than replaces the five region-local triggers;
+the recovery controller still permits only one recovery sequence at a time.
+
+## Services
+
+The Fishing Shop is an instanced scene at the east side of the village plaza.
+Move the complete `FishingShopWorld` instance, not only its booth meshes.
+
+The Pelican perch is decorative signage, not an interaction NPC. Its sign says
+“Sell to Pelicans from the Cooler”; the existing 0.25× Pelican sale remains
+available from the Cooler anywhere in the world. Moving or removing the
+decorative perch does not change that service.
+
+## Temporary by design
+
+All terrain, buildings, docks, reeds, landmarks, signage, palette, and lighting
+are primitive holdover presentation. A future artist or level designer can
+replace `Visuals` and paired static collision without changing fishing,
+recovery, shop, save, economy, or player progression code. Region IDs and
+gameplay volume ownership should remain stable while visuals are replaced.
+
+Water surfaces sit near `y=0.2`; the shared graybox seabed is near `y=-6`.
+There is no structural walkable layer directly below the fishable surfaces.