feat(request): read the app and body from stdin

[yusukebe]

Two stdin features for agents (ideas from Yusuke):

• -d @file reads the request body from a file, -d @- from stdin (curl style)
• Pass - as the file to read the app code from stdin. No boilerplate needed: app is predefined and exported. Code with its own export default is used as-is

echo 'app.get("/hello", (c) => c.json({ ok: true }))' | hono request - -P /hello
cat payload.json | hono request -P /api -X POST -d @-

- also works for routes and ssg through the shared loader. Using - together with -d @- or --watch is an INVALID_OPTION error.

The author should do the following, if applicable

• Add tests
• Run tests
• pnpm run format:fix && pnpm run lint:fix to format the code
• Add TSDoc/JSDoc to document the code