Thinking: gate xhigh by model

src/config/types.ts

@@ -1620,7 +1620,7 @@ export type AgentDefaultsConfig = {
   /** Vector memory search configuration (per-agent overrides supported). */
   memorySearch?: MemorySearchConfig;
   /** Default thinking level when no /think directive is present. */
-  thinkingDefault?: "off" | "minimal" | "low" | "medium" | "high";
+  thinkingDefault?: "off" | "minimal" | "low" | "medium" | "high" | "xhigh";
   /** Default verbose level when no /verbose directive is present. */
   verboseDefault?: "off" | "on";
   /** Default elevated level when no /elevated directive is present. */

src/config/zod-schema.ts

@@ -1242,6 +1242,7 @@ const AgentDefaultsSchema = z
         z.literal("low"),
         z.literal("medium"),
         z.literal("high"),
+        z.literal("xhigh"),
       ])
       .optional(),
     verboseDefault: z.union([z.literal("off"), z.literal("on")]).optional(),