Add a `home-manager` flake input, its nixpkgs following this flake's, and a
`home-manager-module` check that evaluates the real module through
home-manager's standalone entry point and builds the home files derivation
under four operator configurations, asserting on the tree each produces:
the Skill coexisting with an operator's own skills in both the attribute-set
and whole-directory forms, the sibling-enable gate leaving no Skill when
Claude Code is off, and the hook merging into an operator's own SessionStart
list. This is the first automated proof of the module's composition (ADR 0021),
replacing verification by maintainer rebuild.
Reshape the home-manager module so `programs.gitea-axi.enable` installs the
binary always, and the Claude Code context follows the harness. The two
per-artefact toggles and their assertion are replaced by one per-harness
toggle, `enableClaudeCodeIntegration` (default true); its artefacts land only
when `programs.claude-code.enable` is also on, silently absent otherwise.
The Agent Skill is now written through home.file into Claude Code's skills
directory, rather than contributed to `programs.claude-code.skills`, so it
composes with both the attribute-set and whole-directory forms of an operator's
own skills option. The Skill write is gated on `claude-code.enable` explicitly
(keeping package realisation lazy); the hook keeps its sibling-module gate for
free, and the asymmetry is commented. Supersedes three decisions of ADR 0020;
recorded in ADR 0021.
INSTALL.md is updated to the new option surface and the path-form limitation
paragraph removed. Adds the parent spec and the follow-up task 0047 (the flake
check proving composition, implemented separately).
