fix(settings): stagger HTMX model update requests

Add 50ms delay between model dropdown update requests to avoid
HTMX race condition that was dropping the opus request.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: joachimBrindeau

src/claude_code_proxy/ui/templates/settings_modal.html

@@ -176,11 +176,14 @@ <h3 class="text-sm font-semibold text-slate-900 mb-3 flex items-center gap-2">
 function updateModels(event) {
     const provider = event.detail.elt.value
     const tiers = ['sonnet', 'opus', 'haiku']
-    tiers.forEach(tier => {
-        htmx.ajax('GET', `/settings/models-for-provider?provider=${provider}&tier=${tier}`, {
-            target: `#${tier}-select`,
-            swap: 'outerHTML'
-        })
+    // Stagger requests to avoid HTMX race condition
+    tiers.forEach((tier, index) => {
+        setTimeout(() => {
+            htmx.ajax('GET', `/settings/models-for-provider?provider=${provider}&tier=${tier}`, {
+                target: `#${tier}-select`,
+                swap: 'outerHTML'
+            })
+        }, index * 50)
     })
 }
 </script>