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.

scripts/build-panel.mjs

@@ -4,25 +4,22 @@
  * See build/panel.js.
  */
 
-import { readFile, readdir, rename, rm, writeFile } from 'node:fs/promises';
+import { readFile, rename, rm, writeFile } from 'node:fs/promises';
 import { join } from 'node:path';
 import { fileURLToPath } from 'node:url';
-import { build as esbuild } from 'esbuild';
 import { build } from 'vite';
 import standaloneConfig from '../server/standalone/vite.config.js';
 import {
   PANEL_BASE,
   PANEL_OUT_DIR,
   PANEL_WORKER_FILES,
-  PANEL_WORKERS_PATH,
+  PANEL_WORKER_PRELUDE_PATH,
   panelBuildConfig,
   workerFilesPrelude,
-  workersEntrySource,
 } from '../build/panel.js';
 
 const root = fileURLToPath(new URL('../', import.meta.url));
 const outDir = join(root, PANEL_OUT_DIR);
-const cesiumWorkers = join(root, 'node_modules/cesium/Build/Cesium/Workers');
 
 const config = standaloneConfig({ command: 'build', mode: 'production' });
 await build({
@@ -37,26 +34,13 @@ await rm(join(outDir, 'cesium'), { recursive: true, force: true });
 await rename(nested, join(outDir, 'cesium'));
 await rm(join(outDir, PANEL_BASE.split('/')[1]), { recursive: true });
 
-const names = (await readdir(cesiumWorkers))
-  .filter((file) => file.endsWith('.js') && !file.startsWith('chunk-'))
-  .map((file) => file.slice(0, -3));
-const entry = join(outDir, 'cesium', 'workers-entry.js');
-await writeFile(entry, workersEntrySource(names, cesiumWorkers));
-await esbuild({
-  entryPoints: [entry],
-  bundle: true,
-  format: 'iife',
-  minify: true,
-  outfile: join(outDir, PANEL_WORKERS_PATH),
-  logLevel: 'warning',
-});
-await rm(entry);
+// Cesium's workers load these files themselves; embed them in a prelude the
+// panel runs ahead of Cesium's workers script.
 const files = {};
 for (const name of PANEL_WORKER_FILES)
   files[name] = await readFile(join(outDir, 'cesium', name), 'utf8');
-const workers = join(outDir, PANEL_WORKERS_PATH);
 await writeFile(
-  workers,
-  workerFilesPrelude(files) + (await readFile(workers, 'utf8')),
+  join(outDir, PANEL_WORKER_PRELUDE_PATH),
+  workerFilesPrelude(files),
 );
 console.log(`Panel build written to ${PANEL_OUT_DIR}`);