atlas: pixelStorei(UNPACK_FLIP_Y_WEBGL) before texImage2D — the missing line

Diffed our minified bundle against memepool's working one and read both
shaders end-to-end. The math, the slot encoding, the vertex layout, the
texture parameters, the network path — all identical. The one substantive
difference: memepool calls pixelStorei(UNPACK_FLIP_Y_WEBGL, true) before
each canvas-to-texture upload. We didn't.

Without that flag, canvas pixel (x, 0) [the top row, where we drew the
image] lands at texture UV y=0 [the bottom of the texture]. The shader's
`spriteY = atlasSize - spriteY - pxSize` flip then samples the bottom
half of the texture — which is empty — and texture2D returns transparent.
The composite line `base.rgb = tex.rgb * tex.a + vColor.rgb * (1 - tex.a)`
collapses to vColor with tex.a=0, so every textured square rendered as
flat colour, indistinguishable from "no image loaded".

Verified end-to-end via playwright + WebGL FBO readback: the canvas had
the image bytes, the GPU texture had them at the same coords, but the
shader's flipped UV was sampling the empty bottom half. With UNPACK_FLIP_Y_WEBGL=true,
the upload pre-flips so the shader's flip lands on the right region.

Toggling the flag back to false right after the upload to avoid leaking
the state to anything else in the page that might do its own texImage2D.

Author: hans-crypto

frontend/src/app/components/block-overview-graph/_ordpool/ordpool-inscription-atlas.ts

@@ -175,7 +175,15 @@ export class OrdpoolInscriptionAtlas {
     this.gl.activeTexture(this.gl.TEXTURE0 + unit);
     this.gl.bindTexture(this.gl.TEXTURE_2D, this.texture);
     if (this.dirtyTexture) {
+      // HACK -- Ordpool: flip-Y on upload so canvas(x, 0) [top row] lands at
+      // texture UV y=1 [top]. The shader's `spriteY = atlasSize - spriteY -
+      // pxSize` flip then reads the slot region correctly. Without this, every
+      // atlas-sample falls into the empty bottom half of the texture and the
+      // composite produces vColor (flat colored square). Memepool sets the
+      // same flag.
+      this.gl.pixelStorei(this.gl.UNPACK_FLIP_Y_WEBGL, true);
       this.gl.texImage2D(this.gl.TEXTURE_2D, 0, this.gl.RGBA, this.gl.RGBA, this.gl.UNSIGNED_BYTE, this.canvas);
+      this.gl.pixelStorei(this.gl.UNPACK_FLIP_Y_WEBGL, false);
       this.dirtyTexture = false;
     }
   }