Implements StatusModel as a cli.FrameModel that renders a single-line
chain status bar showing height, sync percentage, difficulty, peer
count and tip age. Includes formatAge and formatDifficulty helpers
with SI suffixes. Adds core/cli as a direct dependency.
Co-Authored-By: Charon <charon@lethean.io>
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
