The packaging tier held two kinds of assertion joined only by an
expensive shared setup: the shape of the packed tarball and its
manifest, and the behaviour of the resulting installed binary. Split
them, and teach the second to take the binary it drives from
GITEA_AXI_INSTALLED_BIN.
When that variable names an existing binary the tier drives it and skips
pack-and-install entirely; unset, it packs and installs exactly as
before. The installed-binary facet becomes one seam with two callers —
the npm distribution path today, the Nix installation path in task 0038
— so the two cannot drift apart in what they guarantee about an
installed gitea-axi. Nothing in it may assert on how the binary came to
exist, since store paths, wrapper internals, and the arrangement of the
installed tree are implementation detail of the installation method.
The tarball assertions stay npm-only: no other distribution method
produces a tarball or a packed manifest.
Add the design record for distributing gitea-axi as a Nix flake: a
package, a development shell, and a checks output, plus the continuous
integration changes that come with it.
ADR 0018 records the wrapper's deference to the operator's own `git` and
`tea` — the reverse of the hermetic instinct, chosen because `tea`
refreshes OAuth tokens in place and so must not have two versions
mutating one credential store.
Also records the `tea`-is-still-a-runtime-dependency gotcha, which ADR
0002's title obscures.
