feat(globe): Sharpen on Navara, on at 80 % by default

The contract gains render.setSharpen({ enabled, amount }) and
render.sharpen(). Navara draws it as a custom EffectDesc: Cesium's unsharp
mask (3x3 box blur, gamma 2.2 round trip so one amount matches Cesium)
right after tone mapping and before SMAA/FXAA, skipping sky and cloud
pixels by scene depth. The Cesium engine keeps the state only; Cesium mode
still sharpens with its own post stage, unchanged. The fake engine records
it and the contract suite checks it.

Without a viewer the Sharpen slider and toggle drive the engine with the
same slider-to-amount mapping. On Navara the defaults, presets and share
links read Cesium's 49 % as 80 %.

src/globe/cesium/render.js

@@ -8,6 +8,7 @@ import {
   isRenderGovernorInstalled,
   releaseContinuousRender,
 } from '../../renderGovernor.js';
+import { SHARPEN_INITIAL, mergeSharpen } from '../contract.js';
 
 export const RENDER_OWNER = 'globe-engine';
 
@@ -28,6 +29,7 @@ export function createCesiumRender(
   } = {},
 ) {
   let held = false;
+  let sharpen = { ...SHARPEN_INITIAL };
   const render = {
     request(reason = RENDER_OWNER) {
       requestRender(reason);
@@ -39,6 +41,12 @@ export function createCesiumRender(
     },
     // The scene's real mode: another owner's hold keeps it continuous.
     isContinuous: () => viewer.scene.requestRenderMode === false,
+    // State only: in Cesium mode the app's own post stage sharpens
+    // (src/ui/visualEffects.js), and the scene stays as it was.
+    setSharpen(options) {
+      sharpen = mergeSharpen(sharpen, options);
+    },
+    sharpen: () => ({ ...sharpen }),
   };
   return {
     render,