feat(ai): update all gemini flash models to google/gemini-3-flash-preview

ai.el

@@ -9,15 +9,14 @@
   :defer t
   :config
   ;; Default backend: OpenRouter
-  (setq gptel-model 'google/gemini-3.flash-preview
+  (setq gptel-model 'google/gemini-3-flash-preview
         gptel-backend
         (gptel-make-openai "OpenRouter"
           :host "openrouter.ai"
           :endpoint "/api/v1/chat/completions"
           :stream t
           :key "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"
-          :models '(google/gemini-3.flash-preview
-                    google/gemini-2.5-flash
+          :models '(google/gemini-3-flash-preview
                     x-ai/grok-4.1-fast
                     x-ai/grok-code-fast-1
                     google/gemini-3-pro-preview
@@ -68,7 +67,7 @@
   ;; Quick answers preset
   (gptel-make-preset 'quick
     :description "Quick, concise answers"
-    :model 'google/gemini-2.5-flash
+    :model 'google/gemini-3-flash-preview
     :system "Provide quick, concise answers. Be direct and to the point.")
 
   ;; Documentation writer preset