fix: restore Flash/Pro buttons, add GPT-5.4 label in topbar

- Restore Flash/Pro dual model buttons in GeminiInput (they control
  speed/quality mode sent to backend, not model name)
- Restore selectedModel/onSelectedModelChange props in GeminiInput
- Reset default model back to "pro" in GeminiChat
- Replace Gemini model dropdown in GeminiTopbar with static "GPT-5.4"
  label to show current model name

Co-Authored-By: Claude Sonnet 4.6 (1M context) <noreply@anthropic.com>

frontend/components/gemini/GeminiChat.tsx

@@ -72,7 +72,7 @@ export function GeminiChat() {
   const [extensions, setExtensions] = useState<Extension[]>(INITIAL_EXTENSIONS);
   const [ticketSummary, setTicketSummary] = useState<TicketSummaryData | null>(null);
   const [activeTools, setActiveTools] = useState<Set<string>>(new Set());
-  const [selectedModel, setSelectedModel] = useState<"flash" | "pro">("flash");
+  const [selectedModel, setSelectedModel] = useState<"flash" | "pro">("pro");
   const messagesEndRef = useRef<HTMLDivElement>(null);
   const abortRef = useRef<AbortController | null>(null);
 
@@ -383,6 +383,8 @@ export function GeminiChat() {
           isLoading={isLoading}
           activeTools={activeTools}
           onActiveToolsChange={setActiveTools}
+          selectedModel={selectedModel}
+          onSelectedModelChange={setSelectedModel}
         />
       </div>
 

frontend/components/gemini/GeminiInput.tsx

@@ -27,6 +27,8 @@ interface GeminiInputProps {
   isLoading?: boolean;
   activeTools: Set<string>;
   onActiveToolsChange: (tools: Set<string>) => void;
+  selectedModel: "flash" | "pro";
+  onSelectedModelChange: (model: "flash" | "pro") => void;
 }
 
 const TOOLS: Tool[] = [
@@ -43,6 +45,8 @@ export function GeminiInput({
   isLoading,
   activeTools,
   onActiveToolsChange,
+  selectedModel,
+  onSelectedModelChange,
 }: GeminiInputProps) {
   const textareaRef = useRef<HTMLTextAreaElement>(null);
   const fileInputRef = useRef<HTMLInputElement>(null);
@@ -200,13 +204,32 @@ export function GeminiInput({
             </div>
           </div>
 
-          {/* Bottom row: Model indicator */}
+          {/* Bottom row: Model selector */}
           <div className="flex items-center justify-end px-4 pb-3 pt-0 gap-2">
-            <span
-              className="px-3 py-1.5 rounded-full text-xs font-medium bg-[var(--gem-blue)] text-white"
+            <button
+              onClick={() => onSelectedModelChange("flash")}
+              className={cn(
+                "px-3 py-1.5 rounded-full text-xs font-medium transition-all duration-150 cursor-pointer",
+                selectedModel === "flash"
+                  ? "bg-[var(--gem-blue)] text-white"
+                  : "bg-[var(--gem-surface-2)] text-[var(--gem-text-muted)] hover:bg-[var(--gem-surface-3)] hover:text-[var(--gem-text)]"
+              )}
+              aria-pressed={selectedModel === "flash"}
             >
-              gpt-5.4
-            </span>
+              Flash
+            </button>
+            <button
+              onClick={() => onSelectedModelChange("pro")}
+              className={cn(
+                "px-3 py-1.5 rounded-full text-xs font-medium transition-all duration-150 cursor-pointer",
+                selectedModel === "pro"
+                  ? "bg-[var(--gem-purple)] text-white"
+                  : "bg-[var(--gem-surface-2)] text-[var(--gem-text-muted)] hover:bg-[var(--gem-surface-3)] hover:text-[var(--gem-text)]"
+              )}
+              aria-pressed={selectedModel === "pro"}
+            >
+              Pro
+            </button>
           </div>
 
           {/* Tools panel (collapsible, below input) */}

frontend/components/gemini/GeminiTopbar.tsx

@@ -1,7 +1,6 @@
 "use client";
 
-import { useState } from "react";
-import { Menu, ChevronDown, Settings, Sun, Moon } from "lucide-react";
+import { Menu, Settings, Sun, Moon } from "lucide-react";
 import { useTheme } from "next-themes";
 import { cn } from "@/lib/utils";
 
@@ -10,16 +9,7 @@ interface GeminiTopbarProps {
   onToggleSidebar: () => void;
 }
 
-const models = [
-  "Gemini 2.0 Flash",
-  "Gemini 1.5 Pro",
-  "Gemini 1.5 Flash",
-  "Gemini Advanced",
-];
-
 export function GeminiTopbar({ sidebarOpen, onToggleSidebar }: GeminiTopbarProps) {
-  const [selectedModel, setSelectedModel] = useState("Gemini 2.0 Flash");
-  const [modelDropdownOpen, setModelDropdownOpen] = useState(false);
   const { theme, setTheme } = useTheme();
 
   return (
@@ -42,60 +32,13 @@ export function GeminiTopbar({ sidebarOpen, onToggleSidebar }: GeminiTopbarProps
         <Menu size={20} />
       </button>
 
-      {/* Center: model selector */}
-      <div className="relative">
-        <button
-          onClick={() => setModelDropdownOpen((prev) => !prev)}
-          className="flex items-center gap-1.5 px-4 py-1.5 rounded-full border border-[var(--gem-border)] text-[var(--gem-text)] text-sm font-medium hover:bg-[var(--gem-surface-2)] transition-colors duration-150 cursor-pointer"
-          aria-haspopup="listbox"
-          aria-expanded={modelDropdownOpen}
-          aria-label="选择模型"
-        >
-          <span>{selectedModel}</span>
-          <ChevronDown
-            size={14}
-            className={cn(
-              "text-[var(--gem-text-muted)] transition-transform duration-200",
-              modelDropdownOpen && "rotate-180"
-            )}
-          />
-        </button>
-
-        {/* Dropdown */}
-        {modelDropdownOpen && (
-          <>
-            <div
-              className="fixed inset-0 z-10"
-              onClick={() => setModelDropdownOpen(false)}
-              aria-hidden="true"
-            />
-            <ul
-              role="listbox"
-              className="absolute top-full left-1/2 -translate-x-1/2 mt-2 w-52 bg-[var(--gem-surface-2)] border border-[var(--gem-border)] rounded-2xl shadow-2xl overflow-hidden z-20 py-1.5"
-              aria-label="可用的模型"
-            >
-              {models.map((model) => (
-                <li key={model} role="option" aria-selected={selectedModel === model}>
-                  <button
-                    onClick={() => {
-                      setSelectedModel(model);
-                      setModelDropdownOpen(false);
-                    }}
-                    className={cn(
-                      "w-full text-left px-4 py-2.5 text-sm transition-colors duration-150 cursor-pointer",
-                      selectedModel === model
-                        ? "text-[var(--gem-blue)] bg-[var(--gem-surface)]"
-                        : "text-[var(--gem-text)] hover:bg-[var(--gem-surface-3)]"
-                    )}
-                  >
-                    {model}
-                  </button>
-                </li>
-              ))}
-            </ul>
-          </>
-        )}
-      </div>
+      {/* Center: model label */}
+      <span
+        className="px-4 py-1.5 rounded-full border border-[var(--gem-border)] text-[var(--gem-text)] text-sm font-medium"
+        aria-label="当前模型"
+      >
+        GPT-5.4
+      </span>
 
       {/* Right: theme toggle + settings + avatar */}
       <div className="flex items-center gap-1">