Remove wall spots

Wall spots were markers for where SteamVR panels/windows could dock on a
home's walls (Meta's WallPlacementComponent). Removed the feature end to
end: the WorldWallSpot type and its JSON/binary serialization, the loader
that read WallPlacementComponent, auto-generation of spots and the hotspots
placed in front of them, the Studio editor's Wall Spot kind (Add menu,
properties, overlay draw, picking, selection, report), the debug overlay,
the home report counts, and the walktest viz. The PanelDock subsystem
(src/panel_dock.h) existed only to dock panels onto wall spots and is
deleted with its use in Frame Home's frame loop.

Baked scene format is bumped to v14: new bakes omit wall spots, and older
baked scenes still load (the wall-spot block is read past). Collision walls
(WorldCollider::Wall) are unaffected — only the panel-placement markers are
gone. Docs updated.

Note: the pre-existing FRAME_HOME_PC Windows build break in walkgrid.h
(the `near` macro) is unrelated and left as-is.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

docs/environments-and-fenv.md

@@ -24,7 +24,7 @@ There are two kinds:
 | `fenv.json` | every `.fenv` | The manifest: name, where the home came from (package and version of each `.apk`), and which other members are there. It also holds the environment's own settings. |
 | `scene.bin.lz` | baked | The baked scene, packed with LZMA (much smaller than ZIP's own packing for textures). It is unpacked once, into a cache, then loaded from there. |
 | `apks/...` | wrapped | The original Meta home files (a room, and maybe its vista) |
-| `world.json` | wrapped | The world layer: spawn points, seats, teleport hotspots, walkable surfaces, wall spots, gravity zones. A baked scene carries this inside `scene.bin`. |
+| `world.json` | wrapped | The world layer: spawn points, seats, teleport hotspots, walkable surfaces, gravity zones. A baked scene carries this inside `scene.bin`. |
 | `edits.json` | when you edited | What you changed in Studio: moved and deleted objects, the added sound and how loud the home's own sound plays |
 | a sound file | when you added one | The sound you added in Studio (`.ogg`, `.opus`, `.wav`, `.mp3`, `.flac`), named in `edits.json` |
 | `thumb.png` | usually | The picture the Environments panel shows |

docs/studio-guide.md

@@ -114,7 +114,6 @@ edges, grey are floors you can't reach. **W** shows or hides it.
 | **Seat** | a place to sit: point at it and pull the trigger; its "stand up here" ring is where you get up |
 | **Teleport Hotspot** | a spot the teleport arc snaps to |
 | **Surface** | a box you can scale into a floor, a step or a wall |
-| **Wall Spot** | where SteamVR's panels dock |
 | **Invisible Wall** | stops you; never drawn on the headset. Scale and turn it to fit; where it stands is no longer walkable |
 | **Gravity Zone** | inside it, "down" is the zone's own: a direction, or any surface you stand on |
 

docs/using-frame-home.md

@@ -157,7 +157,7 @@ Frame Home restarts.
 | Item | What it does |
 |---|---|
 | View | Normal, Wireframe (every triangle edge), Meshes (each in its own colour), GPU cost (green is cheap, red is costly), Overdraw (bright where surfaces pile up) |
-| World layer | Shows where you can walk (green), surfaces and colliders, spawns, seats, wall spots and gravity zones |
+| World layer | Shows where you can walk (green), surfaces and colliders, spawns, seats and gravity zones |
 | See-through surfaces | Leave out glass, water, glow and fog, to see whether they're what's slow |
 | Cut-out surfaces | Leave out leaves, grass and fences |
 | Sky | Leave out the sky |