refactor(keyword-detector): inject keywords on every message (#99)

Remove first-message-only restriction and move keyword injection to chat.message
hook for consistent keyword presence across all messages.

🤖 GENERATED WITH ASSISTANCE OF [OhMyOpenCode](https://github.com/code-yeongyu/oh-my-opencode)

src/index.ts

@@ -410,7 +410,6 @@ const OhMyOpenCodePlugin: Plugin = async (ctx) => {
       await rulesInjector?.event(input);
       await thinkMode?.event(input);
       await anthropicAutoCompact?.event(input);
-      await keywordDetector?.event(input);
       await agentUsageReminder?.event(input);
       await interactiveBashSession?.event(input);