fix(model-routing): keep selected models strict (#5801)

Co-authored-by: Alexandre Teixeira <111787685+alteixeira20@users.noreply.github.com>

static/js/settings.js

@@ -448,7 +448,7 @@ async function initDefaultChat() {
   var fbContainer = el('set-defaultFallbacks');
   var addFbBtn = el('set-defaultAddFallback');
   var _endpoints = [];
-  var _fallbacks = []; // [{endpoint_id, model}] — tried in order if primary fails
+  var _fallbacks = []; // Hidden legacy DOM hook; stored values are not loaded or saved.
 
   function enabledEndpoints() {
     return _endpoints.filter(function(e) { return e.is_enabled; });
@@ -534,11 +534,6 @@ async function initDefaultChat() {
     var settings = await res.json();
     if (settings.default_endpoint_id) epSel.value = settings.default_endpoint_id;
     refreshModels(settings.default_model || '');
-    _fallbacks = Array.isArray(settings.default_model_fallbacks)
-      ? settings.default_model_fallbacks.map(function(f) {
-          return { endpoint_id: (f && f.endpoint_id) || '', model: (f && f.model) || '' };
-        })
-      : [];
     renderFallbacks();
   } catch (e) { console.warn('Failed to load default chat settings', e); }
 
@@ -547,13 +542,11 @@ async function initDefaultChat() {
 
   async function saveDefault() {
     try {
-      var clean = _fallbacks.filter(function(f) { return f.endpoint_id && f.model; });
       await fetch('/api/auth/settings', { method: 'POST', credentials: 'same-origin',
         headers: { 'Content-Type': 'application/json' },
         body: JSON.stringify({
           default_endpoint_id: epSel.value,
-          default_model: modelSel.value,
-          default_model_fallbacks: clean
+          default_model: modelSel.value
         })
       });
       msg.textContent = 'Saved'; msg.style.color = 'var(--fg)';