fix(ui-map): render-on-demand + drop pan inertia to stop the Safari fog freeze

The Phase 29 visibility fog ("visible hyperspace") froze the whole UI on
large reports in Safari while staying smooth in Firefox. Root cause: the
fog is a layered overpaint (torus mode = 9 world-sized rects + 9xN
near-world-sized opaque circles, ~270 fills for KNNTS041) and Pixi's
continuous auto-render loop re-rasterised all of it every frame, even
while idle. Safari's WebGPU backend cannot sustain that fillrate, so the
main thread/compositor starved and the entire UI froze.

Stage 1 (vector-preserving, no rasterisation):

- Stop Pixi's auto-render loop (app.stop()) and paint on demand via a
  single Ticker.shared flush gated on viewport.dirty (camera) plus an
  internal requestRender() from every content mutation (fog / hide-set /
  extras / wrap mode / resize / pick overlay). An idle map now does zero
  GPU work per frame; plain hover paints nothing.
- Remove the decelerate (drag-inertia) plugin: a released drag stops
  instantly (owner request) and the viewport goes idle immediately.
- Expose RendererHandle.getRenderCount() / getMapRenderCount for
  deterministic e2e assertions.

Tests: new map-toggles e2e specs (idle map does not repaint; released
drag does not coast) green on all four Playwright projects incl. WebKit.
Docs: renderer.md (render-on-demand section; fog section corrected to the
current single-fogLayer model; FPS note) and PLAN.md Phase 29 decision 8.

If Safari pan is still heavy after this, stage 2 will cut the overpaint
itself with an inverse stencil mask of the circle union (kept vector).

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

ui/frontend/src/lib/active-view/map.svelte

@@ -72,6 +72,7 @@ preference the store already manages.
 		registerMapModeProvider,
 		registerMapPickStateProvider,
 		registerMapPrimitivesProvider,
+		registerMapRenderCountProvider,
 		type MapCameraSnapshot,
 		type MapFogSnapshot,
 		type MapPickStateSnapshot,
@@ -536,12 +537,16 @@ preference the store already manages.
 			const detachMode = registerMapModeProvider(() =>
 				handle === null ? null : handle.getMode(),
 			);
+			const detachRenderCount = registerMapRenderCountProvider(() =>
+				handle === null ? null : handle.getRenderCount(),
+			);
 			detachDebugProviders = (): void => {
 				detachPrim();
 				detachPick();
 				detachCamera();
 				detachFog();
 				detachMode();
+				detachRenderCount();
 			};
 			mountedTurn = report.turn;
 			mountedGameId = targetGameId;

ui/frontend/src/lib/debug-surface.svelte.ts

@@ -74,12 +74,14 @@ type PickStateProvider = () => MapPickStateSnapshot;
 type CameraProvider = () => MapCameraSnapshot | null;
 type FogProvider = () => MapFogSnapshot;
 type ModeProvider = () => WrapMode | null;
+type RenderCountProvider = () => number | null;
 
 let primitivesProvider: PrimitivesProvider | null = null;
 let pickStateProvider: PickStateProvider | null = null;
 let cameraProvider: CameraProvider | null = null;
 let fogProvider: FogProvider | null = null;
 let modeProvider: ModeProvider | null = null;
+let renderCountProvider: RenderCountProvider | null = null;
 
 /**
  * registerMapPrimitivesProvider attaches a provider that yields the
@@ -152,6 +154,23 @@ export function registerMapModeProvider(provider: ModeProvider): () => void {
 	};
 }
 
+/**
+ * registerMapRenderCountProvider attaches a provider that yields the
+ * renderer's actual painted-frame count. Because the renderer runs
+ * render-on-demand, the count stays flat while the map is idle and
+ * only advances on camera moves or content mutations. e2e specs use
+ * it to assert the idle map does not keep repainting. Same idempotent
+ * semantics as the other providers.
+ */
+export function registerMapRenderCountProvider(
+	provider: RenderCountProvider,
+): () => void {
+	renderCountProvider = provider;
+	return () => {
+		if (renderCountProvider === provider) renderCountProvider = null;
+	};
+}
+
 const EMPTY_PICK_STATE: MapPickStateSnapshot = {
 	active: false,
 	sourcePlanetNumber: null,
@@ -191,6 +210,13 @@ export function getMapMode(): WrapMode | null {
 	return modeProvider?.() ?? null;
 }
 
+/** Pulls the renderer's painted-frame count. Returns `null` when no
+ * map view is mounted. Stays constant on idle frames (render-on-demand)
+ * and advances only on camera moves or content mutations. */
+export function getMapRenderCount(): number | null {
+	return renderCountProvider?.() ?? null;
+}
+
 interface RendererDebugWindow {
 	__galaxyDebug?: {
 		getMapPrimitives?: () => readonly MapPrimitiveSnapshot[];
@@ -198,6 +224,7 @@ interface RendererDebugWindow {
 		getMapCamera?: () => MapCameraSnapshot | null;
 		getMapFog?: () => MapFogSnapshot;
 		getMapMode?: () => WrapMode | null;
+		getMapRenderCount?: () => number | null;
 		[key: string]: unknown;
 	};
 }
@@ -222,6 +249,7 @@ export function installRendererDebugSurface(): () => void {
 		getMapCamera,
 		getMapFog,
 		getMapMode,
+		getMapRenderCount,
 	};
 	win.__galaxyDebug = surface;
 	return (): void => {
@@ -245,5 +273,8 @@ export function installRendererDebugSurface(): () => void {
 		if (current.getMapMode === getMapMode) {
 			delete current.getMapMode;
 		}
+		if (current.getMapRenderCount === getMapRenderCount) {
+			delete current.getMapRenderCount;
+		}
 	};
 }