fix: sessions_sspawn model override ignored for sub-agents

Fix bug where sessions_spawn model parameter was ignored, causing sub-agents
   to always use the parent's default model.

   The allowAny flag from buildAllowedModelSet() was not being captured or used.

   🤖 AI-assisted (Claude) - fully tested locally

   Fixes #17479, #6295, #10963

src/commands/agent.ts

@@ -390,6 +390,7 @@ export async function agentCommand(
     let allowedModelKeys = new Set<string>();
     let allowedModelCatalog: Awaited<ReturnType<typeof loadModelCatalog>> = [];
     let modelCatalog: Awaited<ReturnType<typeof loadModelCatalog>> | null = null;
+    let allowAnyModel = false;
 
     if (needsModelCatalog) {
       modelCatalog = await loadModelCatalog({ config: cfg });
@@ -401,6 +402,7 @@ export async function agentCommand(
       });
       allowedModelKeys = allowed.allowedKeys;
       allowedModelCatalog = allowed.allowedCatalog;
+      allowAnyModel = allowed.allowAny ?? false;
     }
 
     if (sessionEntry && sessionStore && sessionKey && hasStoredOverride) {
@@ -412,7 +414,7 @@ export async function agentCommand(
         const key = modelKey(normalizedOverride.provider, normalizedOverride.model);
         if (
           !isCliProvider(normalizedOverride.provider, cfg) &&
-          allowedModelKeys.size > 0 &&
+          !allowAnyModel &&
           !allowedModelKeys.has(key)
         ) {
           const { updated } = applyModelOverrideToSessionEntry({
@@ -439,7 +441,7 @@ export async function agentCommand(
       const key = modelKey(normalizedStored.provider, normalizedStored.model);
       if (
         isCliProvider(normalizedStored.provider, cfg) ||
-        allowedModelKeys.size === 0 ||
+        allowAnyModel ||
         allowedModelKeys.has(key)
       ) {
         provider = normalizedStored.provider;