feat: allow hook model overrides

src/config/types.ts

@@ -216,6 +216,8 @@ export type HookMappingConfig = {
     | "signal"
     | "imessage";
   to?: string;
+  /** Override model for this hook (provider/model or alias). */
+  model?: string;
   thinking?: string;
   timeoutSeconds?: number;
   transform?: HookMappingTransform;

src/config/zod-schema.ts

@@ -743,6 +743,7 @@ const HookMappingSchema = z
       ])
       .optional(),
     to: z.string().optional(),
+    model: z.string().optional(),
     thinking: z.string().optional(),
     timeoutSeconds: z.number().int().positive().optional(),
     transform: z