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/terminal/webview/terminal-emulator-webview-entry.ts

@@ -18,6 +18,8 @@ interface MountMessage {
   initialSnapshot: TerminalState | null;
   scrollbackLines: number;
   theme: ITheme;
+  fontFamily?: string;
+  fontSize?: number;
   pendingModifiers: PendingTerminalModifiers;
   swipeGesturesEnabled: boolean;
 }
@@ -33,6 +35,7 @@ type InboundMessage =
   | { type: "resize"; streamKey: string; shouldClaim?: boolean }
   | { type: "setTheme"; streamKey: string; theme: ITheme }
   | { type: "setScrollback"; streamKey: string; lines: number }
+  | { type: "setFont"; streamKey: string; fontFamily?: string; fontSize?: number }
   | { type: "setPendingModifiers"; streamKey: string; pendingModifiers: PendingTerminalModifiers }
   | { type: "setSwipeGesturesEnabled"; streamKey: string; enabled: boolean }
   | {
@@ -227,6 +230,8 @@ class TerminalWebViewBridge {
       MountMessage | { type: "unmount" } | { type: "resolveLocalFileLinkResponse" }
     >,
   ): void {
+    if (this.receiveConfigurationMessage(message)) return;
+
     switch (message.type) {
       case "writeOutput":
         this.runtime?.write({ data: encodeTerminalOutput(message.text) });
@@ -246,19 +251,34 @@ class TerminalWebViewBridge {
       case "resize":
         this.runtime?.resize({ force: true, shouldClaim: message.shouldClaim !== false });
         break;
+    }
+  }
+
+  private receiveConfigurationMessage(
+    message: Exclude<
+      InboundMessage,
+      MountMessage | { type: "unmount" } | { type: "resolveLocalFileLinkResponse" }
+    >,
+  ): boolean {
+    switch (message.type) {
       case "setTheme":
         this.applyThemeBackground(message.theme);
         this.runtime?.setTheme({ theme: message.theme });
-        break;
+        return true;
       case "setScrollback":
         this.runtime?.setScrollback({ lines: message.lines });
-        break;
+        return true;
+      case "setFont":
+        this.runtime?.setFont({ fontFamily: message.fontFamily, fontSize: message.fontSize });
+        return true;
       case "setPendingModifiers":
         this.runtime?.setPendingModifiers({ pendingModifiers: message.pendingModifiers });
-        break;
+        return true;
       case "setSwipeGesturesEnabled":
         this.swipeGesturesEnabled = message.enabled;
-        break;
+        return true;
+      default:
+        return false;
     }
   }
 
@@ -300,6 +320,8 @@ class TerminalWebViewBridge {
       initialSnapshot: message.initialSnapshot,
       scrollback: message.scrollbackLines,
       theme: message.theme,
+      fontFamily: message.fontFamily,
+      fontSize: message.fontSize,
     });
     sendToNative({ type: "rendererReady", streamKey: message.streamKey, isReady: true });
   }