Run the worker prelude ahead of Cesium's own workers script

Cesium's script sets CESIUM_WORKERS itself when it loads, so the panel's
combined workers script was never used, and neither was the embedded
terrain-heights file: the worker still requested it from the panel
page's site. The panel build now writes only the prelude, and the panel
puts it ahead of whatever Cesium assigns to CESIUM_WORKERS. The separate
esbuild bundle of Cesium's workers is gone.

build/panel.js

@@ -1,16 +1,16 @@
 /**
  * The MCP Apps panel build. A panel loads the app through its MCP server,
  * one tool call per file (see src/tools/globePanel.js), so the app must be
- * few files: one app script, one stylesheet, Cesium's own script, and
- * Cesium's workers combined into one script that Cesium runs from memory.
- * The build is served at PANEL_BASE next to the app.
+ * few files: one app script, one stylesheet, and Cesium's own script, which
+ * carries its workers and starts them from memory. The build is served at
+ * PANEL_BASE next to the app.
  */
 
 // The panel loads these paths (src/tools/globePanel.js); a test keeps the
 // two in step.
 export const PANEL_BASE = '/panel/';
-/** Cesium's workers as one script, relative to the panel build. */
-export const PANEL_WORKERS_PATH = 'cesium/workers.js';
+/** The script the panel runs ahead of Cesium's workers (workerFilesPrelude). */
+export const PANEL_WORKER_PRELUDE_PATH = 'cesium/worker-prelude.js';
 export const PANEL_OUT_DIR = 'dist/panel';
 
 /** A browser Vite config changed to produce the panel build. */
@@ -32,19 +32,6 @@ export function panelBuildConfig(config) {
   };
 }
 
-/**
- * Source for Cesium's `CESIUM_WORKERS` script: every worker module, each
- * evaluated only when Cesium starts that worker. `workerNames` are the
- * module names in Cesium's Workers directory, without `.js`.
- */
-export function workersEntrySource(workerNames, workersDir) {
-  const entries = workerNames.map(
-    (name) =>
-      `  ${JSON.stringify(name)}: () => import(${JSON.stringify(`${workersDir}/${name}.js`)}),`,
-  );
-  return `self.CesiumWorkers = {\n${entries.join('\n')}\n};\n`;
-}
-
 const CONTENT_TYPES = {
   '.css': 'text/css',
   '.geojsonl': 'application/geo+json-seq',