cherry host: production static server + precompression

**On hold until required** (user decision 2026-08-21). `cherry host`: a production-grade static server verb, distinct from `serve` (no drafts, no livereload, no watcher). Scope when picked up: ETags/conditional requests, Range, HEAD, cache-control policy (long for assets, short for HTML), themed 404, access log in the serve --verbose format, /healthz, graceful shutdown, dual-stack. Companion feature that helps every host: optional build-time `.br`/`.gz` precompressed siblings, emitted deterministically, served via content negotiation. Non-goals: TLS termination and rate limiting (a proxy or tunnel owns those). Audience is VPS/homelab/docker-compose self-hosters and a container entrypoint; CDN routes (#11, GitHub Pages) remain the default recommendation for public sites.

Start at the `cherry host` entry point and compare its intended behavior with `serve`, including the `serve --verbose` access-log format. Define the host behavior for conditional requests, ranges, HEAD, caching, 404s, `/healthz`, shutdown, dual-stack, and negotiated `.br`/`.gz` siblings; it is done when these requirements and the container entrypoint work without adding TLS or rate limiting.

Written by the indexing model from the issue text.