ci(data-deploy): build the index with relaton-cli instead of Jekyll

[andrew2net]

Draft — do not enable the gem mode org-wide until relaton-cli is released with relaton index. The git mode (below) works today for piloting.

What

Replace the Jekyll-based data-deploy.yml build with a single relaton index invocation. relaton-cli reads the data repo's ./data folder and emits a self-contained, crawler-indexable index that inlines a compiled Vue+Tailwind bundle.

Companion to relaton/relaton#83 (which added relaton index).

Two source modes (source input)

• gem (default) — gem install relaton-cli and run it. Ruby only; the released gem ships the precompiled frontend bundle. This is the steady-state path once relaton-cli is published.
• git — check out relaton/relaton, compile the frontend on the fly (needs Node), and bundle relaton + relaton-cli from the checkout with pubid from git main (which relaton's code currently tracks). This lets a repo pilot the new index before any gem release.

Why git mode needs Node: relaton-cli's frontend/dist/ is gitignored (built at gem-release time), so a GitHub checkout must compile it (npm ci && npm run build). The gem path avoids Node because the published gem already contains the bundle.

Note: relaton index reads the data YAML directly and never invokes pubid, so the pubid pin only matters for loading relaton cleanly, not for the index output.

Compatibility

• Stays on: workflow_call with no required inputs — existing callers (uses: …/data-deploy.yml@main) are unchanged and get gem mode.
• Optional inputs: source, title, data-dir, mode, relaton-cli-version (gem), relaton-repo / relaton-ref (git).
• Deploy job and default-branch gating (incl. the v2 fix) unchanged.

Pilot a repo on GitHub today

jobs:
  deploy:
    uses: relaton/support/.github/workflows/data-deploy.yml@<this-branch>
    with:
      source: git         # optionally: relaton-ref: main, title: "BIPM Index"

Rollout / blockers

1. gem mode blocker: gem install relaton-cli must resolve to a version that has relaton index. That release hasn't happened yet; the current line is a prerelease (3.0.0.pre.alpha.1), which gem install skips by default — so pin it via relaton-cli-version (or use --pre) until a stable release. Don't switch repos to gem mode org-wide before then.
2. Shared workflow = all repos flip at once on merge. Prefer a gradual rollout: pilot relaton-data-bipm with source: git, verify, then move others.
3. Config no longer consumed: repos' _config.yml / Gemfile.deploy are unused. Titles derive from the repo name (<FLAVOR> Index) unless the caller passes title:.

Verification

Locally, relaton index --flavor bipm cloned relaton-data-bipm, auto-detected the v2 branch, and indexed 7,936 documents with correct raw-YAML links; the generated index.html carries the crawler DOM + embedded JSON + inlined bundle. Workflow YAML lints clean.