feat: remove mock/claude backends, default to gemini, add openai toggle

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

server/routes.py

@@ -34,14 +34,14 @@ class ChatRequest(BaseModel):
     message: str = Field(..., min_length=1)
     history: list[ChatMessage] = Field(default_factory=list)
     mentions: list[str] = Field(default_factory=list)
-    backend: str = "mock"
+    backend: str = "gemini"
     design_state: dict = Field(default_factory=dict)
 
 
 class ReportRequest(BaseModel):
     part_name: str = "part"
     history: list[ChatMessage] = Field(default_factory=list)
-    backend: str = "mock"
+    backend: str = "gemini"
 
 
 # ── Endpoints ──────────────────────────────────────────────────────────────

web/index.html

@@ -1087,9 +1087,8 @@
     </div>
     <div class="topbar-right">
       <div class="backend-toggle">
-        <button id="btn-mock" class="active" onclick="setBackend('mock')">MOCK</button>
-        <button id="btn-gemini" onclick="setBackend('gemini')">GEMINI</button>
-        <button id="btn-claude" onclick="setBackend('anthropic')">CLAUDE</button>
+        <button id="btn-gemini" class="active" onclick="setBackend('gemini')">GEMINI</button>
+        <button id="btn-openai" onclick="setBackend('openai')">OPENAI</button>
       </div>
       <button class="gallery-btn" onclick="openGallery()">
         <svg width="14" height="14" viewBox="0 0 24 24" fill="none" stroke="currentColor" stroke-width="2"><rect x="3" y="3" width="7" height="7" rx="1"/><rect x="14" y="3" width="7" height="7" rx="1"/><rect x="3" y="14" width="7" height="7" rx="1"/><rect x="14" y="14" width="7" height="7" rx="1"/></svg>
@@ -1243,7 +1242,7 @@
 <script>
 // ── STATE ─────────────────────────────────────────────
 
-let currentBackend = 'mock';
+let currentBackend = 'gemini';
 let chatHistory = [];
 let designState = {};
 let chatPanelOpen = true;
@@ -1434,9 +1433,8 @@ function loadSTL(url) {
 
 function setBackend(name) {
   currentBackend = name;
-  document.getElementById('btn-mock').classList.toggle('active', name === 'mock');
   document.getElementById('btn-gemini').classList.toggle('active', name === 'gemini');
-  document.getElementById('btn-claude').classList.toggle('active', name === 'anthropic');
+  document.getElementById('btn-openai').classList.toggle('active', name === 'openai');
 }
 
 // ── CHAT PANEL TOGGLE ─────────────────────────────────