ui/phase-19: ship-group decoder + map binding + selection store

Wires Phase 19's data and rendering layers without yet adding the
inspector UI:

  - game-state.ts grows ReportLocalShipGroup / ReportOtherShipGroup
    / ReportIncomingShipGroup / ReportUnidentifiedShipGroup /
    ReportLocalFleet types and walks the matching FlatBuffers
    vectors (LocalGroup, OtherGroup, IncomingGroup,
    UnidentifiedGroup, LocalFleet) inside decodeReport. The Tech
    map is folded into the fixed-shape ShipGroupTech struct;
    cargo strings normalise to the closed CargoLoadType | "NONE"
    union; UUIDs come back as canonical 36-char strings.
  - synthetic-report.ts mirrors the new fields so the DEV-only
    lobby loader can feed JSON produced by legacy-report-to-json
    straight into the live UI surface.
  - selection.svelte.ts widens its discriminated union with a
    `kind: "shipGroup"` branch carrying a ShipGroupRef
    (local UUID / other / incoming / unidentified by index).
  - world.ts adds Style.strokeDashPx and render.ts.drawLine
    honours it via manual segmentation (PixiJS v8 has no native
    dash API). Ignored on points and circles.
  - state-binding.ts now returns { world, hitLookup }: the
    hit-lookup map keys every primitive id back to a concrete
    HitTarget so the click handler can dispatch to selectPlanet
    or selectShipGroup. Ship-group primitives live in a separate
    ship-groups.ts that emits one point per local / other /
    unidentified group, plus a dashed origin→destination line +
    clickable point per incoming group. Position is interpolated
    along the trajectory for in-hyperspace groups.
  - map.svelte threads the hitLookup into handleMapClick.

Vitest:
  - tests/helpers/empty-ship-groups.ts exposes EMPTY_SHIP_GROUPS
    so existing fixtures can spread the new five empty arrays
    without enumerating every field.
  - state-binding-groups.test.ts covers each group variant's
    primitive geometry and lookup correctness.
  - All previously-existing fixture builders pick up the spread
    so GameReport stays a complete object.

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

ui/frontend/src/map/render.ts

@@ -702,10 +702,29 @@ function drawCircle(g: Graphics, p: CirclePrim, theme: Theme): void {
 }
 
 function drawLine(g: Graphics, p: LinePrim, theme: Theme): void {
-	g.moveTo(p.x1, p.y1);
-	g.lineTo(p.x2, p.y2);
 	const color = p.style.strokeColor ?? theme.lineStroke;
 	const alpha = p.style.strokeAlpha ?? 1;
 	const width = p.style.strokeWidthPx ?? 1;
+	const dash = p.style.strokeDashPx;
+	if (dash === undefined || dash <= 0) {
+		g.moveTo(p.x1, p.y1);
+		g.lineTo(p.x2, p.y2);
+		g.stroke({ color, alpha, width });
+		return;
+	}
+	// PixiJS v8 has no native dashed-line API; segment the path into
+	// equal-length dashes (dash and gap both `dash` units).
+	const dx = p.x2 - p.x1;
+	const dy = p.y2 - p.y1;
+	const length = Math.hypot(dx, dy);
+	if (length === 0) return;
+	const ux = dx / length;
+	const uy = dy / length;
+	const step = dash * 2;
+	for (let t = 0; t < length; t += step) {
+		const segEnd = Math.min(t + dash, length);
+		g.moveTo(p.x1 + ux * t, p.y1 + uy * t);
+		g.lineTo(p.x1 + ux * segEnd, p.y1 + uy * segEnd);
+	}
 	g.stroke({ color, alpha, width });
 }