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>

ui/frontend/src/map/world.ts

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+// Data model for the map renderer.
+//
+// World coordinates are TypeScript numbers (float64). The world is a
+// rectangle [0, W) × [0, H). When wrap mode is 'torus', the world
+// behaves toroidally — primitives near the right edge are visible at
+// the left edge once the camera scrolls past, etc. When wrap mode is
+// 'no-wrap', the world is a bounded plane and the camera is clamped
+// at its edges.
+//
+// The algorithm specification for hit-test, torus wrap, and no-wrap
+// camera behaviour lives in ui/docs/renderer.md. See that document
+// before changing the contract of the types in this file.
+
+export type PrimitiveID = number;
+
+export type WrapMode = "torus" | "no-wrap";
+
+// Style describes the visual appearance of a primitive. Any field may
+// be omitted; missing fields fall back to the active theme defaults.
+export interface Style {
+	fillColor?: number; // 0xRRGGBB
+	fillAlpha?: number; // 0..1
+	strokeColor?: number; // 0xRRGGBB
+	strokeAlpha?: number; // 0..1
+	strokeWidthPx?: number; // pixels at any zoom
+	pointRadiusPx?: number; // pixels at any zoom (for kind === 'point')
+}
+
+// PrimitiveBase carries the fields shared by every primitive kind.
+//
+// priority is used for deterministic ordering during hit-test: higher
+// priority wins ties. hitSlopPx is an optional per-primitive override
+// of the kind default, in screen pixels.
+export interface PrimitiveBase {
+	id: PrimitiveID;
+	priority: number;
+	style: Style;
+	hitSlopPx: number; // 0 = use kind default
+}
+
+export interface PointPrim extends PrimitiveBase {
+	kind: "point";
+	x: number;
+	y: number;
+}
+
+export interface CirclePrim extends PrimitiveBase {
+	kind: "circle";
+	x: number;
+	y: number;
+	radius: number; // world units
+}
+
+export interface LinePrim extends PrimitiveBase {
+	kind: "line";
+	x1: number;
+	y1: number;
+	x2: number;
+	y2: number;
+}
+
+export type Primitive = PointPrim | CirclePrim | LinePrim;
+
+export type PrimitiveKind = Primitive["kind"];
+
+// Default hit slop in screen pixels per primitive kind. Chosen for
+// touch ergonomics; per-primitive `hitSlopPx` overrides the default.
+export const DEFAULT_HIT_SLOP_PX: Record<PrimitiveKind, number> = {
+	point: 8,
+	circle: 6,
+	line: 6,
+};
+
+// kindOrder is the deterministic tie-break order used during hit-test
+// when two primitives match a cursor at identical priority and
+// distance. Smaller value wins.
+export const KIND_ORDER: Record<PrimitiveKind, number> = {
+	point: 0,
+	line: 1,
+	circle: 2,
+};
+
+// Camera describes the world point at the centre of the viewport and
+// the scale (pixels per world unit). Pan/zoom mutate this struct;
+// `pixi-viewport` keeps its own internal state and we mirror it here
+// for hit-test and for tests that read camera state directly.
+export interface Camera {
+	centerX: number;
+	centerY: number;
+	scale: number;
+}
+
+export interface Viewport {
+	widthPx: number;
+	heightPx: number;
+}
+
+// World is the immutable container of primitives plus the toroidal
+// dimensions. The renderer reindexes nothing — the brute-force
+// hit-test walks all primitives on every pointer event, which is
+// adequate for the ~1000-primitive Phase 9 budget.
+export class World {
+	readonly width: number;
+	readonly height: number;
+	readonly primitives: Primitive[];
+
+	constructor(width: number, height: number, primitives: Primitive[] = []) {
+		if (!(width > 0) || !(height > 0)) {
+			throw new Error(`World: width and height must be positive, got ${width}×${height}`);
+		}
+		this.width = width;
+		this.height = height;
+		this.primitives = primitives;
+	}
+}
+
+// Theme carries the default colours used when a primitive's `style`
+// leaves a colour unset. Phase 9 ships a single dark theme; runtime
+// theme switching is deferred to Phase 35.
+export interface Theme {
+	background: number;
+	pointFill: number;
+	circleStroke: number;
+	lineStroke: number;
+}
+
+export const DARK_THEME: Theme = {
+	background: 0x0a0e1a,
+	pointFill: 0xe8eaf6,
+	circleStroke: 0x4fc3f7,
+	lineStroke: 0xa5d6a7,
+};