Vercel preview policy — `docs/site`

Why this PR adds a 7-line vercel.json to docs/site/.

What changed

+ docs/site/vercel.json

{
  "$schema": "https://openapi.vercel.sh/vercel.json",
  "git": {
    "deploymentEnabled": {
      "main": true
    }
  }
}

Why

Audit of the Yonatan-HQ Vercel team in May 2026 found ~497 preview deploys across 11 projects in the prior 30 days, with no documented standard. Single-developer org; nobody is reviewing preview URLs. All preview spend is waste.

Specific to this project: the dashboard already has createDeployments=disabled set on the Vercel side, but PR-triggered deploys still happen anyway (4 dependabot PRs from 2026-05-04 each created previews). A repo-pinned vercel.json is the durable kill — it overrides whatever the dashboard does on PR builds.

Before / after

Before

main → prod PR → preview dependabot → preview

69 preview builds in last 30 days.

After

main → prod PR → ⏭ skipped dependabot → ⏭ skipped

Only push-to-main triggers a build.

Cross-org context

This PR is one of nine in a fan-out implementing Yonatan-HQ/platform#2597 (ADR-002). Same pattern, same one-line config across the Vercel team's projects.

Verification

# Push to non-main branch — no Vercel deploy
git checkout -b throwaway && git commit --allow-empty -m "test" && git push

# Push to main — prod deploy fires
git checkout main && git push

Rollback

Revert the file or change the value to { "deploymentEnabled": true } to allow preview deploys again. No infra side-effects to undo.

Vercel preview policy — docs/site