Upload tile delta to GPU (#4159)

## Description

Reduces the amount of tile data sent to the gpu each tick, roughly
~10fps rate increase on 10 year old chromebook.

Two changes to the territory rendering path:

### 1. Split `passEnabled.mapOverlay` into four flags

The single `mapOverlay` toggle controlled four unrelated passes
(territory fill, border compute, border stamp, trail). Splits it into
`territory`, `borderCompute`, `borderStamp`, `trail` so each can be
toggled independently in the debug GUI. Pure rename — default behavior
is unchanged (all four default to `true`).

### 2. GPU scatter for per-frame tile texture updates

Replaces the dirty-row bbox `texSubImage2D` upload in `TerritoryPass`
with a new `TileScatterPass` that uploads a small attribute buffer of
`(x, y, state)` patches and runs a single `POINTS` draw into an FBO
bound to `tileTex`. Each patch rasterizes as a 1×1 point into exactly
its target texel.

**Why:** the old path's cost scaled with the bounding box of the dirty
rows, not the number of changed tiles. In typical play, tile changes are
spread across the whole map (multiple players fighting in different
regions, scattered trails/fallout), so the bbox covered most of the
map's rows and we re-uploaded mostly-unchanged data every frame. The new
path is constant cost in patch count regardless of spatial distribution,
and no longer scales with map size.

The full-upload path (initial load / seek / spawn-phase flush) is
unchanged. `fullUploadPending` correctly supersedes any queued scatter
patches.

## Please complete the following:

- [x] I have added screenshots for all UI updates *(N/A — no UI
changes)*
- [x] I process any text displayed to the user through translateText()
and I've added it to the en.json file *(N/A — no user-facing text)*
- [x] I have added relevant tests to the test directory *(renderer code,
not covered by unit tests; verified visually)*

## Please put your Discord username so you can be contacted if a bug or
regression is found:

evan

src/client/render/gl/render-settings.json

@@ -1,7 +1,10 @@
 {
   "passEnabled": {
     "terrain": true,
-    "mapOverlay": true,
+    "territory": true,
+    "borderCompute": true,
+    "borderStamp": true,
+    "trail": true,
     "territoryPatterns": true,
     "structure": true,
     "unit": true,