M0.5: detailed scenery, mountain/sea-cliff boundary, Godot 4.7

Scenery (all procedural, seeded, no imported assets):
- Terrain shader: grass/dry grass/dirt/sand/rock strata/snow + detail normals
- 5 tree types, faceted mossy rocks, cliff outcrops, sea stacks, bushes,
  logs and stumps, batched as MultiMesh per 48 m cell
- Wind-animated grass and flowers streamed in tiles around the player
- Lake (depth-shaded water with shore foam), ocean to the horizon,
  cloud sky shader, volumetric fog, glow, softer shadows
- Swimming: float at the surface, swim-jump to climb out

World bounds:
- Steep mountain rim with an invisible wall partway up; one side opens to
  a sheer sea cliff with the wall 1 m inside the edge; whole chunk is an
  island so the mesh edge is never visible
- Respawn safety net if the player leaves the walkable area or the map
- Fix: the cliff edge now tracks the wall in the headlands (it used to
  drop away inside the wall, leaving a pit with lake water hanging over it)

Tests: tests/test_boundary.gd (24-direction escape attempt) and
tests/test_terrain_edges.gd (no ground below waterline near the wall).

Upgrades the project to Godot 4.7 (project.godot rewritten by the 4.7
importer, .uid files added) and documents it in the setup guide.

docs/SETUP_ON_NEW_MACHINE.md

@@ -7,7 +7,19 @@ download — the M0 world is generated in code.
 ## 1. Install Godot 4.3+
 - **macOS / Windows / Linux:** download the *standard* build (NOT the .NET/C#
   build — this project is pure GDScript) from https://godotengine.org/download
-- Any 4.3.x or newer 4.x works. The project was built on `4.3.stable`.
+- Use **4.7.x or newer 4.x**. The project was upgraded to `4.7.2.stable` (an
+  older editor will warn that the project is from a newer version).
+- macOS shortcut: `brew install --cask godot`. If Homebrew can't unpack it,
+  download the zip from the GitHub release page and move `Godot.app` to
+  `/Applications`.
+
+## Tests
+```bash
+# Boundary: tries to walk/jump out of the valley in 24 directions
+godot --headless --path . --fixed-fps 30 --script res://tests/test_boundary.gd
+# Terrain: no pits/hanging water just inside the boundary wall
+godot --headless --path . --script res://tests/test_terrain_edges.gd
+```
 
 ## 2. Get the project onto the machine
 You have the folder (from the zip, or a git remote). Then:
@@ -41,8 +53,8 @@ WASD move · Mouse look · Shift sprint · Space jump · ESC frees the cursor.
   first open. Don't copy it between machines.
 - If scripts look like they "didn't load", let the first editor open finish its
   import pass, then press play.
-- Where we are: **M0 complete** (walkable lit world). Next is **M1** (gather →
-  craft → build). See `docs/ROADMAP.md`.
+- Where we are: **M0 + M0.5 complete** (detailed, bounded island valley). Next
+  is **M1** (gather → craft → build). See `docs/ROADMAP.md`.
 
 ## Recommended: push to a git remote for cross-machine work
 A zip is a one-time snapshot. For going back and forth between machines, create a