feat(tanstack-migrator): flag -tanstack repos as cfworkers-builds in catalog

[JonasJesus42]

Sets metadata.platform = "cfworkers-builds" on the migrated repo's row in the decocms sites catalog so the deco Fresh/Deno k8s deployer stops watching the -tanstack repo (today it keeps trying to deploy it and leaves a broken deployment).

setSitePlatform does a guarded read-merge-write on the single row matched by github_repo_url — it never clobbers other metadata keys, never throws, and no-ops when the catalog isn't configured or the row isn't indexed yet (so it can't block a migration). It's auto-applied at creating_repo (early, best-effort) and re-asserted at deploy (once the repo is indexed); the new SITE_SET_PLATFORM tool applies it on demand to existing -tanstack sites the bot is already fighting. Uses the existing DECOCMS_SUPABASE_KEY (service-role).

Stacked on add-decofile-sync-workflow-tool; typecheck + tests green.

🤖 Generated with Claude Code

---

Summary by cubic

Mark migrated -tanstack repos as Cloudflare Workers Builds in the decocms sites catalog to stop the Fresh/Deno k8s deployer from watching and redeploying them. Applied automatically during repo creation and again after deploy, with a tool to backfill existing sites.

• New Features

  • Added a guarded, idempotent read-merge-write that sets metadata.platform = "cfworkers-builds" without clobbering other metadata, matches exact owner/name, and returns { ok, reason } instead of throwing.
  • Auto-applied in the creating_repo and deploying_cf phases; logs events and warns only on unexpected failures; never blocks the migration.
  • New operator tool SITE_SET_PLATFORM to flag a specific siteId or owner/name; default platform is cfworkers-builds; returns { ok, repo, platform, reason }.

• Migration

  • Set DECOCMS_SUPABASE_URL and DECOCMS_SUPABASE_KEY (service-role) to enable catalog writes.
  • Run SITE_SET_PLATFORM for existing -tanstack repos the bot is currently trying to deploy.

^{Written for commit 9a4b1fb. Summary will update on new commits.}