fix(models): land #31202 normalize custom provider keys (@stakeswky)

Landed from contributor PR #31202 by @stakeswky.

Co-authored-by: stakeswky <stakeswky@users.noreply.github.com>

src/agents/models-config.providers.ts

@@ -496,6 +496,13 @@ export function normalizeProviders(params: {
 
   for (const [key, provider] of Object.entries(providers)) {
     const normalizedKey = key.trim();
+    if (!normalizedKey) {
+      mutated = true;
+      continue;
+    }
+    if (normalizedKey !== key) {
+      mutated = true;
+    }
     let normalizedProvider = provider;
     const configuredApiKey = normalizedProvider.apiKey;
 
@@ -554,7 +561,19 @@ export function normalizeProviders(params: {
       normalizedProvider = antigravityNormalized;
     }
 
-    next[key] = normalizedProvider;
+    const existing = next[normalizedKey];
+    if (existing) {
+      // Keep deterministic behavior if users accidentally define duplicate
+      // provider keys that only differ by surrounding whitespace.
+      mutated = true;
+      next[normalizedKey] = {
+        ...existing,
+        ...normalizedProvider,
+        models: normalizedProvider.models ?? existing.models,
+      };
+      continue;
+    }
+    next[normalizedKey] = normalizedProvider;
   }
 
   return mutated ? next : providers;