v0.3.0

Byte/comment preservation becomes its own flag, decoupled from backend
selection.

Added

• --preserve / -p flag for byte/comment-preserving reads. It turns on
  fidelity mode with the default backend, so yqr -p '.' file.yaml reproduces
  the input byte-for-byte — comments, quoting, indentation, and line endings
  survive.
• A runnable demo showcase under docs/content/demo/ (yqr-demo.sh plus sample
  deploy.yaml / config.yaml inputs) walking through navigation, iteration,
  pipes, raw output, and preserve mode.

Changed

• --engine now selects the backend parser only and no longer implies
  preservation. It picks which library performs a --preserve read (default
  noyalib); whether to preserve is --preserve's job. Without --preserve,
  --engine has no observable effect.

Breaking

• --engine noyalib '.' no longer preserves bytes on its own — use
  --preserve (optionally with --engine noyalib to name the backend
  explicitly). This decouples backend choice from fidelity mode.