feat(setup): install/uninstall primary commands; adopt/unadopt aliases

[potiuk]

Now that Magpie can be installed from agent marketplaces (#907), "install" is the more familiar term than "adopt." This makes install/uninstall the primary command surface, with adopt/unadopt kept as aliases (nothing breaks for anyone using them).

Changes

• /magpie-setup install — first-time install (the default no-arg action); /magpie-setup adopt is a documented alias.
• /magpie-setup uninstall — reverses it; /magpie-setup unadopt is a documented alias.
• Renamed skills/setup/adopt.md → install.md, skills/setup/unadopt.md → uninstall.md, and docs/setup/unadopt.md → uninstall.md; all path references repointed.
• Updated the skill's argument-hint, sub-action list, and command table.

Deliberately kept

• The "adopter" / "adopter repo" noun (the ecosystem role) — unchanged.
• The "Adopt a Magpie" landing-page slogan.
• Deep internal prose still uses "adopt" informally (a valid alias) — the full verb reword is PR B (follow-up).

Scope: command surface + file renames only. Part of the adoption→installation terminology shift discussed on the list.

[potiuk]

Looking for reviews :)

[milamberspace]

Reviewed the full diff (24 files), CI, and the current state of main. This is a clean, backward-compatible terminology refactor — nicely done. Verified that every file on main referencing adopt.md / unadopt.md is repointed here, so the rename leaves no dangling links, and the renames preserve history. CI is all green.

Two things before merge:

1. Rebase needed — the PR is currently conflicting. main has moved since this branched: #902 (Codex CLI runtime) edited adopt.md and unadopt.md after the branch point, which creates a rename/edit conflict. The good news is #902 added no new references to the old filenames elsewhere, so the rebase is just folding its content edits into the renamed install.md / uninstall.md.

2. Consistency nit in skills/setup/SKILL.md. The line

   Main-checkout-only sub-actions (adopt, upgrade, unadopt) …

   still names the old primaries. It's harmless (they're valid aliases), but for consistency with making install/uninstall primary it'd read better as install, upgrade, uninstall.

Process checks (per AGENTS.md): since this touches skills, worth confirming the setup eval suite still passes (a pure rename shouldn't move behavior, but the rule asks for it) and that tools/spec-loop/.last-sync is current before pushing the rebase.

Nothing blocking on the substance — LGTM once rebased and the SKILL.md line is updated.

[choo121600]

looks good :)

[milamberspace]

Reviewed the command-surface change and the renames — the dispatch logic looks right: no-arg → install.md, and install / adopt both route to install.md (adopt as a documented alias), same for uninstall / unadopt. Backward compatibility is preserved, and the repointed anchors (#local-self-adoption-methodlocal, #step-5, #step-12) all resolve in the renamed install.md. No broken links within the PR's own tree.

One thing that will bite on rebase, though: docs/rfcs/RFC-AI-0007.md landed on main after this branch's point, and line 184 still links to the old filename:

- [`skills/setup/SKILL.md`](../../skills/setup/SKILL.md),
  [`adopt.md`](../../skills/setup/adopt.md),
  [`upgrade.md`](../../skills/setup/upgrade.md) — the flow this RFC rewires.

Once this PR is rebased onto current main, that becomes a dangling link and the lychee link-check hook fails in CI. .gitignore:9 carries the same stale reference (see skills/setup/adopt.md → "Local self-adoption") — cosmetic, but worth fixing in the same pass. Both just need repointing to install.md. I confirmed the CI failure reproduces by cherry-picking the three commits onto a current-main-based branch.

Minor (probably your "PR B" scope): a couple of command-token spots in skills/setup/SKILL.md still name the alias rather than the primary — line 404 Main-checkout-only sub-actions (adopt, upgrade, unadopt) and line 439 *(unadopt only)*. Non-blocking.

Otherwise this reads well and the install/uninstall surface is a clear improvement. Happy to see it land once the rebase repoints those two references.