feat: add frosted glass appearance and improve local MCP recovery

Add an opt-in persistent frosted glass setting for the top bar and runtime checklist, with chat scrolling behind the header while preserving scroll anchors and window controls.

Retry transient local MCP initialization failures once after cleanup, include redacted connection diagnostics in feedback, and index lifecycle events to reduce execution statistics scans.

Release note: Add optional frosted glass appearance with chat visible behind the title bar; improve local tool connection recovery and diagnostic feedback.

src/shared/application-settings-contracts.ts

@@ -59,6 +59,7 @@ const applicationPreferencesSchema = z
   .object({
     checkUpdatesOnStartup: z.boolean(),
     desktopNotificationsEnabled: z.boolean().default(true),
+    transparentFrostedEffectEnabled: z.boolean().default(false),
     updateSource: updateSourceSchema,
     modelDownloadSource: modelDownloadSourceSchema,
     localToolEnvironment: localToolEnvironmentSettingsSchema,
@@ -90,6 +91,7 @@ export const applicationSettingsUpdateSchema = applicationPreferencesSchema
   .extend({
     applicationNavigation: applicationNavigationSchema.optional(),
     desktopNotificationsEnabled: z.boolean().optional(),
+    transparentFrostedEffectEnabled: z.boolean().optional(),
     localInferenceEnabled: z.boolean().optional(),
     magicNotesEnabled: z.boolean().optional(),
     heartbeatEnabled: z.boolean().optional(),

src/shared/goodbuddy-config-contracts.test.ts

@@ -153,6 +153,7 @@ describe('GoodBuddy configuration contracts', () => {
       application: {
         checkUpdatesOnStartup: true,
         desktopNotificationsEnabled: true,
+        transparentFrostedEffectEnabled: false,
         updateSource: 'github',
         modelDownloadSource: 'modelscope',
         localToolEnvironment: defaultLocalToolEnvironmentSettings,