feat(ui): Implement theme persistence and system preference support

Adds comprehensive theme management across the application, allowing users to save their preferred color scheme (light/dark) or automatically follow the operating system's settings. This required updating state management in App.svelte to handle theme loading and applying changes dynamically via CSS variables.

The styling layer was significantly updated with new CSS variables and rules for both dark and light modes, ensuring visual consistency across all components like dialogs, buttons, and sidebars.

- Added logic to detect system color scheme preference
- Implemented full support for persistent light/dark mode switching
- Overhauled global CSS variables for improved theme adaptability

src/lib/TitleBar.svelte

@@ -24,22 +24,44 @@
   export let onToggleAutoRefresh: () => void = () => {};
   export let onOpenSettings: () => void = () => {};
 
-  const win = getCurrentWindow();
+  let win: ReturnType<typeof getCurrentWindow> | null = null;
   let isMaximized = false;
   let unlisten: (() => void) | undefined;
   let appVersion = "";
 
   onMount(async () => {
-    isMaximized = await win.isMaximized();
-    unlisten = await win.onResized(async () => {
+    try {
+      win = getCurrentWindow();
       isMaximized = await win.isMaximized();
-    });
-    appVersion = await getVersion();
+      unlisten = await win.onResized(async () => {
+        isMaximized = await win?.isMaximized() ?? false;
+      });
+    } catch {
+      win = null;
+    }
+
+    try {
+      appVersion = await getVersion();
+    } catch {
+      appVersion = "";
+    }
   });
 
   onDestroy(() => {
     unlisten?.();
   });
+
+  function minimizeWindow() {
+    void win?.minimize();
+  }
+
+  function toggleMaximizeWindow() {
+    void win?.toggleMaximize();
+  }
+
+  function closeWindow() {
+    void win?.close();
+  }
 </script>
 
 <header class="titlebar" data-tauri-drag-region>
@@ -200,12 +222,12 @@
     <div class="titlebar-divider" aria-hidden="true"></div>
 
     <div class="titlebar-controls">
-      <button class="tb-btn" onclick={() => win.minimize()} title="Minimize" aria-label="Minimize">
+      <button class="tb-btn" onclick={minimizeWindow} title="Minimize" aria-label="Minimize">
         <Minus size={12} aria-hidden="true" />
       </button>
       <button
         class="tb-btn"
-        onclick={() => win.toggleMaximize()}
+        onclick={toggleMaximizeWindow}
         title={isMaximized ? "Restore" : "Maximize"}
         aria-label={isMaximized ? "Restore" : "Maximize"}
       >
@@ -220,7 +242,7 @@
           </svg>
         {/if}
       </button>
-      <button class="tb-btn close" onclick={() => win.close()} title="Close" aria-label="Close">
+      <button class="tb-btn close" onclick={closeWindow} title="Close" aria-label="Close">
         <X size={12} aria-hidden="true" />
       </button>
     </div>

src/lib/components/AppSettingsDialog.svelte

@@ -1,19 +1,22 @@
 <script lang="ts">
   import { Check, Settings, X } from "@lucide/svelte";
-  import type { AnalyticsSettings } from "../types";
+  import type { AnalyticsSettings, AppTheme } from "../types";
 
   interface Props {
     analytics: AnalyticsSettings;
-    onSave: (settings: AnalyticsSettings) => void;
+    theme: AppTheme;
+    onSave: (settings: AnalyticsSettings, theme: AppTheme) => void;
     onClose: () => void;
   }
 
-  let { analytics, onSave = () => {}, onClose = () => {} }: Props = $props();
+  let { analytics, theme = "system", onSave = () => {}, onClose = () => {} }: Props = $props();
 
   let analyticsEnabled = $state(true);
+  let selectedTheme = $state<AppTheme>("system");
 
   $effect(() => {
     analyticsEnabled = analytics.enabled;
+    selectedTheme = theme;
   });
 
   function save() {
@@ -21,7 +24,7 @@
       ...analytics,
       enabled: analyticsEnabled,
       noticeSeen: true,
-    });
+    }, selectedTheme);
   }
 </script>
 
@@ -38,6 +41,31 @@
     </header>
 
     <form class="app-settings-form" onsubmit={(event) => { event.preventDefault(); save(); }}>
+      <section class="settings-section">
+        <header>
+          <Settings size={16} aria-hidden="true" />
+          <div>
+            <span class="eyebrow">Appearance</span>
+            <h3>Theme</h3>
+          </div>
+        </header>
+
+        <div class="settings-segmented" role="radiogroup" aria-label="Theme">
+          <label class:active={selectedTheme === "system"}>
+            <input type="radio" bind:group={selectedTheme} value="system" />
+            <span>System</span>
+          </label>
+          <label class:active={selectedTheme === "light"}>
+            <input type="radio" bind:group={selectedTheme} value="light" />
+            <span>Light</span>
+          </label>
+          <label class:active={selectedTheme === "dark"}>
+            <input type="radio" bind:group={selectedTheme} value="dark" />
+            <span>Dark</span>
+          </label>
+        </div>
+      </section>
+
       <section class="settings-section">
         <header>
           <Settings size={16} aria-hidden="true" />

src/lib/components/RepoLoadingOverlay.svelte

@@ -187,6 +187,47 @@
     animation: bar-slide 1.35s ease-in-out infinite;
   }
 
+  :global(:root[data-theme="light"]) .repo-loading {
+    background:
+      radial-gradient(circle at 50% 42%, rgba(49, 95, 214, 0.12), transparent 34%),
+      linear-gradient(135deg, #f7f9fd 0%, #eef3f9 48%, #f8fafc 100%);
+  }
+
+  :global(:root[data-theme="light"]) .repo-loading-grid {
+    opacity: 0.38;
+    background-image:
+      linear-gradient(rgba(49, 95, 214, 0.1) 1px, transparent 1px),
+      linear-gradient(90deg, rgba(15, 143, 181, 0.08) 1px, transparent 1px);
+  }
+
+  :global(:root[data-theme="light"]) .repo-loading-card {
+    border-color: rgba(61, 89, 142, 0.2);
+    background:
+      linear-gradient(180deg, rgba(255,255,255,0.96), rgba(244,247,252,0.94)),
+      var(--color-surface-raised);
+    box-shadow:
+      0 26px 72px rgba(28,44,74,0.18),
+      inset 0 1px 0 rgba(255,255,255,0.9);
+  }
+
+  :global(:root[data-theme="light"]) .repo-loading-traces .trace {
+    filter: drop-shadow(0 0 8px rgba(49,95,214,0.22));
+  }
+
+  :global(:root[data-theme="light"]) .repo-loading-traces .trace-cut {
+    stroke: rgba(49,95,214,0.34);
+  }
+
+  :global(:root[data-theme="light"]) .repo-loading-icon {
+    filter:
+      drop-shadow(0 18px 24px rgba(28,44,74,0.2))
+      drop-shadow(0 0 18px rgba(49,95,214,0.18));
+  }
+
+  :global(:root[data-theme="light"]) .repo-loading-bar {
+    background: rgba(49,95,214,0.12);
+  }
+
   @keyframes overlay-in { from { opacity: 0; } to { opacity: 1; } }
   @keyframes grid-drift { to { transform: translate3d(42px, 42px, 0); } }
   @keyframes icon-float {

src/lib/types.ts

@@ -10,6 +10,7 @@ export type FileStatusKind =
 export type CommitAiPhase = "idle" | "loading" | "ready" | "error";
 export type CommitAiProvider = "local" | "openai" | "anthropic" | "custom";
 export type CommitAiLocalProfile = "fast" | "balanced" | "detailed";
+export type AppTheme = "system" | "light" | "dark";
 
 export interface CommitAiStatus {
   phase: CommitAiPhase;