Clean the legacy backlog so the tracker-tag lint can become a required
gate (mara's warn-during-cleanup -> full-tree-enforcement path). Rewrite
the ~33 real `closes/see #NNN` provenance refs in doc-comments to prose
across hive-forge, hive-c0re, hive-ag3nt, hive-matrix-mcp, hive-sh4re,
and add a `lint:allow` line marker to check-issue-refs.sh for genuine
non-tracker `#<digits>` (a hash-digit heading-detection test input).
Tree is now lint-clean; tracker-tag lint ready to promote to required.
Add `hivectl gateway {create-user,delete-user,list-users}` subcommands for
managing htpasswd files used by gateway Basic auth. Pure Rust bcrypt
(cost 12, $2y$ prefix nginx accepts). No external htpasswd binary required.
Also fix the NixOS module assertion: `cfg.auth ? htpasswdFile` is always
true in the module system (declared options always exist as keys); switch
to `nullOr path; default = null` + `!= null` check so the assertion
actually fires with a useful error when enable=true but no file is set.
Guard bind-mount and nginx config against null to prevent eval errors.
Update docs/gateway.md to show hivectl commands instead of raw htpasswd.
