fix(games): vendor pixi-filters had absolute import baked in

Post-merge Playwright sweep against the live dev preview revealed 4 games
still 404'ing on /assets/games/vendor/pixi.min.mjs (no path prefix). Trace:
the vendored pixi-filters.min.mjs ships with the absolute path

  import {...} from "/assets/games/vendor/pixi.min.mjs"

baked into its bundle as the peer-dependency reference. This was hidden
behind the lazy import (only oom/prune/quantization/roofline call into
filters), which is why Lander and 9 other games passed.

Fix: sed-replace the absolute string with a sibling-relative path
'./pixi.min.mjs', which resolves correctly regardless of deploy base
since both vendor files live in the same directory.

Verified with full Playwright sweep against locally-rendered _build:
14/14 games now pass — canvas mounted, runtime ready, no errors, no
404s, including the four previously-broken filter-using games.

site/assets/games/vendor/pixi-filters.min.mjs

@@ -6,7 +6,7 @@
  * http://www.opensource.org/licenses/mit-license
  * 
  * Copyright 2025, PixiJS Team, All Rights Reserved
- */import{Filter as f,GpuProgram as c,GlProgram as m,deprecation as h,TexturePool as y,Texture as _,Color as S,BlurFilter as qt,DEG_TO_RAD as G,AlphaFilter as Zt,BlurFilterPass as rn,TextureSource as Ht,ImageSource as Qt,ObservablePoint as Jt,Point as eo,ViewSystem as no}from"/assets/games/vendor/pixi.min.mjs";var p=`in vec2 aPosition;
+ */import{Filter as f,GpuProgram as c,GlProgram as m,deprecation as h,TexturePool as y,Texture as _,Color as S,BlurFilter as qt,DEG_TO_RAD as G,AlphaFilter as Zt,BlurFilterPass as rn,TextureSource as Ht,ImageSource as Qt,ObservablePoint as Jt,Point as eo,ViewSystem as no}from"./pixi.min.mjs";var p=`in vec2 aPosition;
 out vec2 vTextureCoord;
 
 uniform vec4 uInputSize;