Add appearance settings for theme, fonts, and syntax highlighting (#1236)

* Add appearance settings for theme, fonts, and syntax highlighting

New Appearance section in Settings to configure the app theme, UI and
mono font family + size, and a syntax-highlighting theme chosen
independently of light/dark. Font family fields default to empty and
show the active system stack as the placeholder; a live split-diff
preview reflects the choices as they change. The theme picker moves
here from General.

Preferences are client-only (AsyncStorage) and applied at runtime by
patching every registered Unistyles theme via
UnistylesRuntime.updateTheme, so existing StyleSheet consumers repaint
with no per-component preference reads and no useUnistyles. No
daemon/protocol change.

* Expand syntax themes and move the preview under the chooser

Replace the small fixed syntax-theme set with eight popular themes — GitHub,
Catppuccin, Dracula, Tokyo Night, One, Nord, Gruvbox, Solarized — built from a
compact per-theme role palette. The app theme and syntax theme stay separate;
the only coupling is the light/dark axis: a theme with both variants uses its
light palette on a light app and its dark palette on a dark app, while the code
frame (gutter, line numbers, background) keeps following the app theme. Default
is now GitHub (GitHub keeps its existing hand-tuned maps for an exact match).

Move the live preview directly under the syntax-theme chooser, drop the
"preview.ts" filename header, and use a clearer code snippet for it.

* Update settings e2e for the moved theme picker and Appearance section

The theme picker moved from General to the new Appearance section, so the
General-content assertion no longer finds "Theme" — point it at "Default send"
(which stays in General) and add Appearance to the e2e section map plus an
expectAppearanceContent check, and exercise the Appearance section in the
sidebar-navigation test.

* Render the appearance preview as a unified diff

Switch the live preview from side-by-side columns to a single unified diff:
unchanged context lines plus "-"/"+" rows for the change, matching how diffs
read elsewhere in the app. Same snippet, mono font, syntax colors, and live
code-font draft behavior.

* Fix code font size change shrinking all UI text

applyAppearance scaled the live (already-patched) theme ramp instead of the
authored FONT_SIZE ramp, so it was not idempotent: every appearance change
re-scaled the current sizes, compounding the whole-UI font scale. With any
non-default UI size, changing the code size — or any setting — shrank (or grew)
all app text, and it persisted into the theme. Build the ramp from the canonical
FONT_SIZE ramp each apply (code size still set absolutely), so applies are
idempotent and a code-size change never touches the UI ramp.

* Apply the interface font across the app on web

react-native-web stamps a default font onto every text element, so the interface
font only reached the few components that set a font explicitly. Inject one rule
that points all text at a CSS variable (updated live as the setting changes),
with high specificity (1,2,0) so it deterministically beats RN-web's base font
and Unistyles' generated classes — no stylesheet-order fragility. Code, diff, and
monospace surfaces carry a `data-pmono` marker (and their subtrees are excluded),
so they keep their code font.

Web-only: React Native has no global font cascade, so native still applies the UI
font only where components opt in. Inline `code` within chat prose is a known
minor gap (its render paths aren't tagged yet).

* Keep preview code in the code font

* Apply code font settings to terminals

* Fix settings host picker import after rebase

* Format terminal webview bundle

packages/app/src/screens/startup-splash-screen.tsx

@@ -16,11 +16,11 @@ import { BookOpen, Copy, RotateCw, TriangleAlert } from "lucide-react-native";
 import { StyleSheet, useUnistyles } from "react-native-unistyles";
 import { PaseoLogo } from "@/components/icons/paseo-logo";
 import { Button } from "@/components/ui/button";
-import { Fonts } from "@/constants/theme";
 import { getDesktopDaemonLogs, type DesktopDaemonLogs } from "@/desktop/daemon/desktop-daemon";
 import { TitlebarDragRegion } from "@/components/desktop/titlebar-drag-region";
 import { isNative, isWeb } from "@/constants/platform";
 import { useWebScrollbarStyle } from "@/hooks/use-web-scrollbar-style";
+import { CODE_SURFACE_DATASET } from "@/styles/code-surface";
 
 interface StartupSplashScreenProps {
   bootstrapState?: {
@@ -236,7 +236,7 @@ const styles = StyleSheet.create((theme) => ({
     color: theme.colors.destructive,
     fontSize: theme.fontSize.code,
     lineHeight: 20,
-    fontFamily: Fonts.mono,
+    fontFamily: theme.fontFamily.mono,
   },
   logsMeta: {
     color: theme.colors.foregroundMuted,
@@ -257,7 +257,7 @@ const styles = StyleSheet.create((theme) => ({
     padding: theme.spacing[4],
   },
   logsText: {
-    fontFamily: Fonts.mono,
+    fontFamily: theme.fontFamily.mono,
     fontSize: theme.fontSize.code,
     color: theme.colors.foreground,
     lineHeight: 18,
@@ -417,7 +417,9 @@ export function StartupSplashScreen({ bootstrapState }: StartupSplashScreenProps
             GitHub and include the logs below.
           </Text>
 
-          <Text style={styles.errorMessage}>{bootstrapState.splashError}</Text>
+          <Text dataSet={CODE_SURFACE_DATASET} style={styles.errorMessage}>
+            {bootstrapState.splashError}
+          </Text>
 
           {daemonLogs?.logPath ? <Text style={styles.logsMeta}>{daemonLogs.logPath}</Text> : null}
 
@@ -427,7 +429,7 @@ export function StartupSplashScreen({ bootstrapState }: StartupSplashScreenProps
               contentContainerStyle={styles.logsContent}
               showsVerticalScrollIndicator
             >
-              <Text selectable style={styles.logsText}>
+              <Text dataSet={CODE_SURFACE_DATASET} selectable style={styles.logsText}>
                 {logsText}
               </Text>
             </ScrollView>