feat(agent): add assistant model selector

src/app/layout.tsx

@@ -104,6 +104,7 @@ export default async function RootLayout({ children }: { children: React.ReactNo
   let signedIn = false;
   let assistantEnabled = false;
   let assistantName = DEFAULT_ASSISTANT_NAME;
+  let assistantModel: string | null = null;
 
   const session = await auth();
   if (session?.user?.id) {
@@ -117,6 +118,7 @@ export default async function RootLayout({ children }: { children: React.ReactNo
         themeNavStyle: users.themeNavStyle,
         assistantEnabled: users.assistantEnabled,
         assistantName: users.assistantName,
+        assistantModel: users.assistantModel,
       })
       .from(users)
       .where(eq(users.id, session.user.id))
@@ -129,6 +131,7 @@ export default async function RootLayout({ children }: { children: React.ReactNo
       navStyle = row.themeNavStyle as NavStyle;
       assistantEnabled = row.assistantEnabled;
       assistantName = row.assistantName?.trim() || DEFAULT_ASSISTANT_NAME;
+      assistantModel = row.assistantModel?.trim() || null;
     }
     userDashboards = await db
       .select({
@@ -186,6 +189,7 @@ export default async function RootLayout({ children }: { children: React.ReactNo
               configured={isLlmConfigured()}
               userId={session.user.id}
               assistantName={assistantName}
+              assistantModel={assistantModel}
             />
           ) : null}
           <AppToaster position="bottom-right" />