fix(desktop): default UI Scale to 100% and keep chat text at 110%

Fresh installs opened at 90% window zoom, and View > Actual Size (Ctrl/Cmd+0) reset to 90% rather than actual size. Ship 100% as the default UI Scale; Chat Text Size keeps its 110% default.

apps/desktop/DESIGN.md

@@ -346,7 +346,7 @@ so glass and message-bubble transparency do not reveal scrolling text.
 
 ## Chat typography
 
-Appearance → Typography keeps **UI Scale** as whole-window zoom (90% by
+Appearance → Typography keeps **UI Scale** as whole-window zoom (100% by
 default). **Chat Text Size** is a separate desktop-local multiplier (110% by
 default) on conversation text and the composer editor, including floating and
 inline-edit composers.

apps/desktop/e2e/fixtures.ts

@@ -133,11 +133,10 @@ export function createSandbox(prefix: string): Sandbox {
     'utf8',
   )
 
-  // Pin Chromium actual-size zoom (level 0) for the suite. Fresh installs
-  // ship DEFAULT_ZOOM_LEVEL at the Appearance 90% preset, but Playwright
-  // click hit-testing and the committed visual baselines were calibrated at
-  // 100%. Without this file every sandbox would inherit the product default
-  // and fail pointer interception + snapshot diffs.
+  // Pin Chromium actual-size zoom (level 0) for the suite. Playwright click
+  // hit-testing and the committed visual baselines were calibrated at 100%,
+  // so the suite must not drift if the product default (DEFAULT_ZOOM_LEVEL)
+  // ever moves off 100% again.
   fs.writeFileSync(
     path.join(userDataDir, 'zoom-state.json'),
     JSON.stringify({ zoomLevel: 0 }, null, 2),

apps/desktop/electron/zoom.test.ts

@@ -44,6 +44,10 @@ test('level 0 is exactly 100 percent (Chromium actual-size baseline)', () => {
   assert.equal(percentToZoomLevel(100), 0)
 })
 
+test('fresh installs and Actual Size (Ctrl/Cmd+0) land on 100 percent', () => {
+  assert.equal(zoomLevelToPercent(DEFAULT_ZOOM_LEVEL), 100)
+})
+
 test('percentToZoomLevel rejects garbage by falling back to the shipped default', () => {
   assert.equal(percentToZoomLevel(NaN), DEFAULT_ZOOM_LEVEL)
   assert.equal(percentToZoomLevel(0), DEFAULT_ZOOM_LEVEL)

apps/desktop/electron/zoom.ts

@@ -15,7 +15,8 @@ const MAX_ZOOM_LEVEL = 9
 /** Half Chromium's default step; matching the shortcuts and View menu. */
 export const ZOOM_STEP = 0.1
 
-export const DEFAULT_ZOOM_LEVEL = Math.log(0.9) / Math.log(ZOOM_FACTOR_BASE)
+/** 100%: Chromium actual size, so View → Actual Size (Ctrl/Cmd+0) means it. */
+export const DEFAULT_ZOOM_LEVEL = 0
 
 export function clampZoomLevel(value) {
   if (!Number.isFinite(value)) {

apps/desktop/src/store/zoom.ts

@@ -10,7 +10,7 @@
 
 import { atom } from 'nanostores'
 
-export const $zoomPercent = atom<number>(90)
+export const $zoomPercent = atom<number>(100)
 
 export function setZoomPercent(percent: number): void {
   window.hermesDesktop?.zoom?.setPercent(percent)