feat(request): JSON envelope output by default - #87

Move request to the shared JSON envelope (part of #77, same as build in #85).

• Default output is { ok, data: { status, headers, body } }. A JSON response body is embedded as an object, so it is not double-escaped
• -J, --json is gone. --plain prints the raw body like curl (-i / -I work with it)
• A binary body becomes body: null with binary: true. -o / -O now always save the raw body and add savedTo to the output
• Errors are the shared JSON error with exit code 1 (e.g. ENTRY_NOT_FOUND)

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