Onboarding prompt

You are onboarding this repository to sprout (every pull request gets its own
preview database plus an optional preview app).

Step 1 — read the docs first, in this order.
1. https://simpros.github.io/sprout/llms.txt — the index of every doc page.
2. https://simpros.github.io/sprout/docs/adopting-a-repo.md — the
   `.sprout.yaml` manifest reference.
3. https://simpros.github.io/sprout/docs/ci-integration.md — CI wiring for
   this forge (GitLab component or GitHub reusable workflow).
Fetch each URL; do not rely on memory of this product.

Step 2 — inspect the repo before writing anything. Runtime and package
manager, the Dockerfile(s), how migrations run, whether fixtures/seed data
exist, which forge hosts it, and the existing CI workflow files. State what
you found in one short paragraph.

Step 3 — derive, then confirm. Propose `slug` and the preview hostname
template (must contain `{pr_id}`, bare host, no scheme/port/path) from the
repo name and its existing deploy conventions, and ask me to confirm both
before you write them. Never invent a domain or a hostname pattern.

Step 4 — write only these files.
- `.sprout.yaml` — the minimal working config: `slug`, `preview.hostname`,
  plus `health` and `seed`/`db`/`services`/`mail` only where this repo
  actually needs them. Match the manifest keys exactly
  (`unknown key: <path>` rejects typos).
- `Dockerfile.seed` — only if preview data is wanted and no seed image
  exists yet.
- The CI file for this forge: the GitLab one-include component
  (`templates/preview.yml` shape, `sprout_version` pinned) or the GitHub
  caller workflow (`examples/adopting-repo/.github/workflows/sprout.yml`
  shape, `sprout_version` pinned, `contents: read` + `pull-requests: write`
  + `packages: write`).

Step 5 — tell me the CI variables to set myself (names, masked/secret,
where they go): `SPROUT_URL` (gateway URL), `SPROUT_TOKEN` (deploy token
scoped to this repo), optional `SPROUT_APP_ENV` / `SPROUT_SEED_ENV` dotenv
blobs and `GITLAB_TOKEN` for MR notes. Do not create, print, commit or
guess their values. If you cannot find a required value, ask me. Never
deploy against an unverified gateway URL without asking.

Step 6 — verify what you can without a running gateway: run the CLI's own
manifest loader over the file you wrote (`apps/cli/src/yaml.ts`
`parseSproutYaml`) and paste the result. Then name my next step
(`sprout doctor`, then a first `sprout ci preview` run from CI).

Do not:
- rewrite or refactor application code,
- touch files other than the ones in Step 4,
- invent operator-side settings (`SPROUT_PREVIEW_POSTGRES_URL`,
  `SPROUT_TRAEFIK_*`, networks), tokens or endpoints,
- run a deploy or open a PR against a live instance without asking me first.

When you are done, summarise in five lines: files written, values you
confirmed with me, CI variables I must set, commands I should run next,
anything you could not determine.