Fog lit by rays: shadows cut through tiles, and walls stay visible

The fog asked one question per tile -- can I see its centre? -- and drew or
skipped the whole tile on the answer. Every shadow was a staircase, tiles
snapped in and out as you walked, and a wall beside you vanished whenever
its centre happened to sit behind its neighbour.

Visibility casts rays from the eye instead: a fixed sweep, plus two aimed
either side of every wall corner, which is what makes each shadow edge a
straight line rather than a smear between rays. The view now draws terrain
and actors first and then darkness over whatever the rays did not reach,
so a shadow runs straight through a tile and an enemy rounding a corner
appears a slice at a time. Bullets are a child node and are still drawn
over the dark; telegraphs are drawn after it, as they must be.

"A bit less strict" is three specific things. A wall face you can see is
lit 26 units in, measured perpendicular to the face; shadows end in a
short fade rather than a line; and sight fades over its last 64 units
rather than stopping at a circle. Still hard fog -- nothing remembered.

The first version measured that depth along the ray, and a screenshot
caught what no test had: a wall you look along got a sliver, so the wall
beside you in a tunnel looked missing -- the old fog's own complaint.
Perpendicular depth fixes it, and light stops the instant a ray steps
back into the open, so it never rounds a corner, never reaches the far
side of a one-tile wall, and never leaves a stepped wall through its
other face. Two tiles touching only at a corner are closed.

About half a millisecond a frame. Measured against the old fog in the
same scene: hub 68 fps against 62, dungeon 240 against 240. The hub's
own low rate predates this.

MapGrid gains a revision counter so the corner list is rebuilt only when
the map changes or the eye crosses a tile. screenshot.tscn now captures a
dungeon, a tunnel and the tunnel with F1's overlay, which draws where
each ray stopped -- and makes SHOT_DIR rather than failing every capture
when it does not exist.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

CLAUDE.md

@@ -13,7 +13,7 @@ the obvious default.
 
 ```bash
 tools/check.sh      # parse-check every script (~5s) -- run after every edit
-tools/test.sh       # 468 GUT tests, headless (~4s)
+tools/test.sh       # 534 GUT tests, headless (~4s)
 tools/smoke.sh      # real server + 4 bot clients over ENet (~40s)
 tools/server.sh     # dedicated server
 tools/client.sh --listen            # host and play, no menu
@@ -29,7 +29,7 @@ godot --headless --path . res://tools/diag_loot.tscn          # drop -> pick up
 godot --headless --path . res://tools/diag_upgrades.tscn      # level -> choice -> taken at the NPC -> new stats
 godot --headless --path . --script tools/bench.gd             # sim cost per tick
 python3 tools/build_local_assets.py                           # rebuild the local-only bullet atlas
-SHOT_DIR=/tmp/shots godot --path . res://tools/screenshot.tscn # capture the menus and HUD (needs a display)
+SHOT_DIR=/tmp/shots godot --path . res://tools/screenshot.tscn # menus, HUD, roster, and the fog in a dungeon and a tunnel (needs a display)
 ```
 
 `diag_progression`, `diag_loot` and `diag_upgrades` exist because the bot smoke
@@ -243,8 +243,13 @@ ticks in milliseconds with no SceneTree.
   enemies and the boss all go through the same lerp. The boss did not for a
   long time, which is invisible while bosses stand still and looks broken the
   moment one moves.
+- **The fog works by draw order, not by deciding per object.** `WorldView._draw`
+  draws terrain and every actor within sight range, then the darkness from
+  `Visibility` over them, then whatever must stay visible. That is what lets a
+  tile or an enemy be half lit. Anything new that fog may hide goes *before*
+  `_draw_darkness`; anything it must not goes after.
 - **A telegraph must be visible through fog.** `WorldView._draw_telegraphs`
-  ignores line of sight on purpose; everything else in the view respects it. A
+  is drawn after the darkness on purpose; everything else in the view is under it. A
   warning you cannot see is an unavoidable hit with extra steps.
 - **No i-frames.** Every bullet that touches a player lands; `spawn_grace` is
   the only invulnerable state. Do not reintroduce post-hit immunity — it makes