Expose Allium as a local marketplace plugin

[yenda]

Summary

• vendor the Allium plugin package under plugins/allium
• switch the marketplace Allium entry from a remote GitHub source to ./plugins/allium
• include both Claude and Codex plugin manifests so Codex can discover and install allium@juxt-plugins

Verification

• node -e "JSON.parse(require('fs').readFileSync('.claude-plugin/marketplace.json','utf8')); console.log('marketplace json ok')"
• python3 /home/yenda/.codex/skills/.system/plugin-creator/scripts/validate_plugin.py /home/yenda/claude-plugins/plugins/allium
• CODEX_HOME=/tmp/claude-plugins-codex-home codex plugin marketplace add /home/yenda/claude-plugins --json
• CODEX_HOME=/tmp/claude-plugins-codex-home codex plugin list --available --json
• CODEX_HOME=/tmp/claude-plugins-codex-home codex plugin add allium@juxt-plugins --json

Notes

This is the marketplace half of the Codex install fix. The matching Allium repo PR adds the Codex-native manifest and README instructions.

[yavorpanayotov]

Reviewed alongside the repo-side PR (juxt/allium#41). The approach is sound: the marketplace already vendors several plugins as local ./plugins/X entries (chalk, chill, clojure-lsp, code-map), and since Codex discovers only local entries — not remote github sources — switching Allium to ./plugins/allium is the consistent fix. Vendoring both .claude-plugin/ and .codex-plugin/ manifests and flipping the marketplace entry all look right.

One thing to fix before merge — the vendored snapshot is already behind juxt/allium@main:

• plugins/allium/.claude-plugin/plugin.json is missing the lspServers block added in Wire allium-lsp in plugin.json for live .allium diagnostics (#39) allium#48.
• The vendored skills/allium/references/patterns.md and language-reference.md predate Add patterns.md example for calling an external API (#38) allium#46 and #49 (the external-API pattern and zero-argument contract signatures).

Re-vendoring from current main (or a fresh release tag) before merge would keep the Codex copy from lagging the Claude Code one.

Bigger picture — vendoring drift. A local copy needs re-syncing on every Allium release or it silently rots; this PR already demonstrates that. Worth adding a small guard so it can't: a script that copies the plugin payload from a pinned juxt/allium ref, plus a CI check that fails if plugins/allium differs from that ref. Happy to help wire it up.

Thanks for driving the Codex support — the structure here is the right shape.

[yavorpanayotov]

Follow-up: I opened #12, which adds scripts/sync-allium.sh + a CI drift check for the vendored copy.

Two things that help here:

1. Re-vendoring this PR can just be scripts/sync-allium.sh (from Add a sync guard for the vendored Allium plugin #12) instead of a manual copy — it vendors plugins/allium from the pinned juxt/allium ref.
2. The pin in Add a sync guard for the vendored Allium plugin #12 is juxt/allium@229ccd0 (current main), which already includes the lspServers + doc updates this PR's snapshot was missing, and the new .codex-plugin/plugin.json (just merged via Add Codex plugin manifest allium#41). So vendoring from that ref resolves the staleness and gives Codex its manifest in one shot.

Suggested order: re-vendor plugins/allium from 229ccd0 (or scripts/sync-allium.sh once #12 lands), then merge this + #12 together so the drift check goes green.