Generate the CLI reference from vark --help

The CLI reference page is generated straight from vark --help, so every flag and subcommand stays in lockstep with the code:

• No hand-maintained option tables to drift
• Each subcommand is documented from its own --help, examples included
• The page’s front matter is preserved; only its body is rewritten, so titles, nav placement and redirects survive a regeneration

The generated page is a build artifact of the release scripts rather than something to edit by hand — change the command in the CLI and the docs follow. See the CLI reference for the full command list.