feat: Preset reset on Default, expanded fields & cross-modal nav

- Reset presets to system defaults when "Default" is clicked in Configure Models (resetGlobalPresets() + backend reset action)
- Expand preset fields to full config parity: ctx_length, ctx_history/ctx_input, vision, rate limits, kwargs, browser_http_headers
- Extract _normalizePresets() helper inside store to eliminate duplication
- Hide "Edit Presets" link when Per-Chat Override is disabled
- Add Settings + API Keys navigation buttons to Model Presets page
- Add dynamic import guard for plugin-settings-store.js in cross-modal navigation buttons
- Rename model switcher label from "Default" to "Default LLM"

plugins/_model_config/webui/config.html

@@ -11,6 +11,14 @@
        x-init="
          await $store.modelConfig.ensureLoaded();
          $store.modelConfig.initConfigFields(config);
+         const _origReset = context.resetToDefault.bind(context);
+         context.resetToDefault = async () => {
+           const before = context.settings;
+           await _origReset();
+           if (context.settings !== before) {
+             await $store.modelConfig.resetGlobalPresets();
+           }
+         };
        ">
     <template x-if="config && $store.modelConfig._loaded">
       <div class="model-config-sections">
@@ -32,6 +40,13 @@
               </label>
             </div>
           </div>
+
+          <div class="override-presets-link" x-show="config.chat_model.allow_chat_override">
+            <button class="text-button" @click="openModal('/plugins/_model_config/webui/main.html')">
+              <span class="material-symbols-outlined" style="font-size:15px;">tune</span>
+              <span>Edit Presets</span>
+            </button>
+          </div>
         </div>
 
         <!-- Model Sections (Main, Utility, Embedding) -->
@@ -280,6 +295,13 @@
   .model-section .section-title {
     margin-top: 0;
   }
+  .override-presets-link {
+    margin-top: 4px;
+  }
+  .override-presets-link .text-button {
+    font-size: 0.78rem;
+    gap: 4px;
+  }
   .eye-toggle {
     position: absolute;
     right: 8px;