feat: split batch and snapshot into commands

[yusukebe]

--batch and the new snapshot mode rejected almost every single-request option — the sign of separate commands under one flag. Now: hono batch <source> [file] runs JSONL lines, and hono snapshot [file] prints the current behavior as batch lines to stdout (paramless GET routes carry their actual response as expect, plus one probe line for the not-found behavior). The taxonomy: routes never sends a request; request, batch, snapshot exist to send them.

Also fixed on the way: hono snapshot | hono batch - piping (stdin is now read as a stream — the sync read failed with EAGAIN on a pipe), and old --batch/--snapshot flags answer with the new command.

Merge #125 first — I will resolve the overlap here after.

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