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/components/terminal-emulator.tsx

@@ -134,6 +134,8 @@ interface TerminalEmulatorProps {
   testId?: string;
   xtermTheme?: ITheme;
   scrollbackLines: number;
+  fontFamily?: string;
+  fontSize?: number;
   swipeGesturesEnabled?: boolean;
   onSwipeLeft?: () => void;
   onSwipeRight?: () => void;
@@ -215,6 +217,8 @@ export default function TerminalEmulator({
     cursor: "#e6e6e6",
   },
   scrollbackLines,
+  fontFamily,
+  fontSize,
   swipeGesturesEnabled = false,
   onSwipeLeft,
   onSwipeRight,
@@ -236,8 +240,12 @@ export default function TerminalEmulator({
   const hostRef = useRef<HTMLDivElement | null>(null);
   const runtimeRef = useRef<TerminalEmulatorRuntime | null>(null);
   const mountedThemeRef = useRef<ITheme>(xtermTheme);
+  const fontFamilyRef = useRef(fontFamily);
+  const fontSizeRef = useRef(fontSize);
   const scrollbackLinesRef = useRef(scrollbackLines);
   scrollbackLinesRef.current = scrollbackLines;
+  fontFamilyRef.current = fontFamily;
+  fontSizeRef.current = fontSize;
   const viewportRef = useRef<HTMLElement | null>(null);
   const dragStartOffsetRef = useRef(0);
   const dragStartClientYRef = useRef(0);
@@ -486,6 +494,8 @@ export default function TerminalEmulator({
       initialSnapshot: initialSnapshotRef.current,
       scrollback: scrollbackLinesRef.current,
       theme: mountedThemeRef.current,
+      fontFamily: fontFamilyRef.current,
+      fontSize: fontSizeRef.current,
     });
     onRendererReadyChangeRef.current?.({ streamKey, isReady: true });
 
@@ -525,6 +535,10 @@ export default function TerminalEmulator({
     runtimeRef.current?.setPendingModifiers({ pendingModifiers });
   }, [pendingModifiers]);
 
+  useEffect(() => {
+    runtimeRef.current?.setFont({ fontFamily, fontSize });
+  }, [fontFamily, fontSize]);
+
   useEffect(() => {
     if (focusRequestToken <= 0) {
       return () => {};