feat(hooks): add sisyphus-gpt-hephaestus-reminder hook

Shows error toast when Sisyphus runs with a GPT model, nudging user to
use Hephaestus instead.

🤖 Generated with [OhMyOpenCode](https://github.com/code-yeongyu/oh-my-opencode)

src/config/schema/hooks.ts

@@ -37,6 +37,7 @@ export const HookNameSchema = z.enum([
   "delegate-task-retry",
   "prometheus-md-only",
   "sisyphus-junior-notepad",
+  "sisyphus-gpt-hephaestus-reminder",
   "start-work",
   "atlas",
   "unstable-agent-babysitter",