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/speed-history.test.js

@@ -1,6 +1,10 @@
 const test = require('node:test');
 const assert = require('node:assert/strict');
-const { updateSpeedHistory } = require('../lib/speed-history');
+const { updateSpeedHistory, createInitialSpeedHistoryState } = require('../lib/speed-history');
+
+test('initial speed history contains a drawable zero baseline', () => {
+  assert.deepEqual(createInitialSpeedHistoryState(), { display: 0, history: [0, 0] });
+});
 
 test('speed history smooths rising and falling samples independently', () => {
   const state = { display: 0, history: [] };