fix: stabilize the header on first paint

Pass the installed version with the startup language so the renderer can display it before asynchronous initialization.

Seed and start the upload sparkline immediately, keep a fixed update-action slot across all update states, and remove the delayed automatic update check.

Add first-frame regression coverage for version, speed baseline, update geometry, and startup query behavior.

tests/startup-renderer.test.js

@@ -3,7 +3,7 @@ const assert = require('node:assert/strict');
 const { EventEmitter } = require('node:events');
 const fs = require('node:fs');
 const path = require('node:path');
-const { configureStartupRenderer, createStartupWindow, resolveStartupLanguage } = require('../lib/startup-renderer');
+const { configureStartupRenderer, createStartupWindow, resolveStartupLanguage, createStartupQuery } = require('../lib/startup-renderer');
 
 class TestBrowserWindow extends EventEmitter {
   constructor(options) {
@@ -50,6 +50,14 @@ test('resolveStartupLanguage accepts only the supported persisted language', ()
   assert.equal(resolveStartupLanguage(null), 'en');
 });
 
+test('startup query carries language and installed version into the first renderer frame', () => {
+  assert.deepEqual(createStartupQuery({ globalSettings: { language: 'de' } }, '2.1.25'), {
+    language: 'de',
+    version: '2.1.25'
+  });
+  assert.deepEqual(createStartupQuery(null, 'invalid'), { language: 'en', version: '' });
+});
+
 test('createStartupWindow forces the main window to start hidden', () => {
   const startup = createStartupWindow(TestBrowserWindow, { width: 1100, show: true });
 
@@ -124,3 +132,22 @@ test('upload sidebar renders and updates the remaining upload size', () => {
   assert.match(html, /Verbleibende Größe[\s\S]*id="uploadTelemetryRemainingSize"[^>]*>0 B</u);
   assert.match(appSource, /_setUploadTelemetryText\(['"]uploadTelemetryRemainingSize['"],\s*formatBytes\(stats\.bytesRemaining\)\)/u);
 });
+
+test('header occupies its final geometry before asynchronous initialization', () => {
+  const projectRoot = path.join(__dirname, '..');
+  const html = fs.readFileSync(path.join(projectRoot, 'renderer', 'index.html'), 'utf8');
+  const appSource = fs.readFileSync(path.join(projectRoot, 'renderer', 'app.js'), 'utf8');
+  const mainSource = fs.readFileSync(path.join(projectRoot, 'main.js'), 'utf8');
+  const css = fs.readFileSync(path.join(projectRoot, 'renderer', 'styles.css'), 'utf8');
+  const updateButton = html.match(/<button class="header-update-button"[^>]*id="headerUpdateBtn"[^>]*>/u)?.[0] || '';
+  const firstFrameInitialization = appSource.lastIndexOf('\ninitializeStaticHeader();');
+  const asynchronousInitialization = appSource.lastIndexOf('\ninit().then(');
+
+  assert.doesNotMatch(updateButton, /\shidden(?:\s|>)/u);
+  assert.match(css, /\.header-update-button\s*\{[^}]*width:\s*146px;[^}]*flex:\s*0 0 146px;/su);
+  assert.match(css, /\.version-badge\s*\{[^}]*min-width:\s*48px;/su);
+  assert.notEqual(firstFrameInitialization, -1);
+  assert.ok(firstFrameInitialization < asynchronousInitialization);
+  assert.match(mainSource, /createStartupQuery\([^,]+,\s*app\.getVersion\(\)\)/u);
+  assert.doesNotMatch(mainSource, /runAutomaticUpdateCheck\(true\);\s*\},\s*3000\)/u);
+});