Hook payloads typed

Untyped hook payloads — parameters typed as any, unknown, or Record<string, any> — eliminate compile-time safety from every plugin in the ecosystem. Plugin authors get no autocompletion, no error on typos in property names, and no signal when a host update renames a payload field. Breakage appears only at runtime, often in production. ISO 25010 maintainability.analysability scores fall sharply when the API surface cannot be understood without running code; typed payloads are the primary mechanism for making plugin APIs analysable.

Define a typed map of all hook payloads and use generic registration to infer types at call sites. This converts payload shape errors from runtime crashes into compile-time failures, and provides IDE autocompletion to every plugin author.

interface HookPayloads {
  'before:request': { request: Request; config: PluginConfig };
  'after:response': { request: Request; response: Response; duration: number };
  'on:error': { error: Error; request: Request; retryCount: number };
}

on<K extends keyof HookPayloads>(
  hook: K,
  handler: (payload: HookPayloads[K]) => void | Promise<void>
): void;