v1.0.0-rc7

Seventh release candidate: builtin discovery now follows the runtime registry
across the REPL and language server, and the urfave CLI migration is complete.

• Complete REPL discovery. :functions now lists every runtime callable
  instead of a 19-name manual subset. Completion includes registered
  namespaces, members, constants, and every parser keyword, including
  Duration, JSON.parse_as, Math.PI, and unless.
  (#957)
• Qualified builtin signature help. Namespace calls such as
  JSON.parse_as(...) now show their documented signatures. Runtime
  registration is the source of truth for completion, hover, signatures,
  checker contracts, and builtin documentation, with coverage checks
  preventing drift.
  (#957)
• Consistent CLI I/O and cancellation. Commands use urfave's configured
  streams, surface write failures, and propagate Ctrl-C cancellation. lsp
  and repl help also stop advertising unsupported positional arguments.
  (#956)