v0.1.0

First tagged release. shellf provisions targets over SSH via a detached resident
agent that evaluates on the host — "raw shell, but idempotent, previewable, fast."

Added

• Language: lexer, parser, and evaluator with the observe/apply/status def
  contract, if/else, error handling (?), parse-time for loops, and
  with { } per-call variable overrides.
• Idempotent execution with a --check preview and a status mode that reports
  current-vs-desired state per host.
• Templating: template(src, dst) with the @{var} delimiter, rendered per host
  over inventory variables.
• Secrets: --secret-file / --secret-env with value-based redaction in all
  output, and a tmpfs workdir that keeps plaintext off the target's persistent disk.
• Modules: directory-package user defs, local imports, and hash-verified remote git
  modules with shellf.lock and a content-addressed cache.
• Embedded, self-hosted standard library: apt, docker/compose, systemd, ufw, files,
  users, git-sync, http-check, and more.
• SSH transport with a resident agent (inactivity TTL), host-key verification, and
  per-user agent/workdir scoping.
• Commands: run, status, clean, and version.