ui/phase-9: PixiJS map renderer with torus and no-wrap modes

Stand up the vector map renderer in ui/frontend/src/map/ on top of
PixiJS v8 + pixi-viewport@^6. Torus mode renders nine container
copies for seamless wrap; no-wrap mode pins the camera at world
bounds and centres on an axis when the viewport exceeds the world
along that axis. Hit-test is a brute-force pass with deterministic
[-priority, distSq, kindOrder, id] ordering and torus-shortest
distance, validated by hand-built unit cases.

The development playground at /__debug/map exposes a window
debug surface for the Playwright spec, which forces WebGPU on
chromium-desktop, WebGL on webkit-desktop, and accepts the
auto-picked backend on mobile projects.

Algorithm spec lives in ui/docs/renderer.md, which also pins the
new deprecation status of galaxy/client (the entire Fyne client
module, including client/world). client/world/README.md and the
Phase 9 stub in ui/PLAN.md gain matching deprecation banners.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

client/world/README.md

@@ -1,5 +1,12 @@
 # World rendering package
 
+> **Deprecated.** This package belongs to the deprecated
+> `galaxy/client` Fyne client. New code must not import it. The
+> active map renderer lives in `ui/frontend/src/map/` (TypeScript
+> + PixiJS), with its specification in `ui/docs/renderer.md`. The
+> sources here remain for historical context only and are not the
+> reference algorithm for the new renderer.
+
 ## Purpose
 
 `world` is the client-side map model and renderer for a 2D world that normally