Discover bounded app Roots and the API-owned build route

The project runtime plan for one commit. detected: no runtime is stored yet and this commit selects it; confirmed: the commit matches the stored runtime; change-required: the commit needs the detected runtime and deploys only after an explicit sourceBuildEngineChange; stored-engine-blocked: this commit cannot deploy, and blocker carries its reason: either the stored runtime cannot admit it, or a build Job already detected it as a Workers app (detectedEngine workers-v1) that cannot run, which is refused with its fix and never built on Paketo. detectedEngine workers-v1 without a stored runtime is the route: the Workers build Job detects the runtime before any user code runs, then builds on Workers, builds the same deployment on Paketo, or refuses it. Warnings (from the last build Job detection for this commit, and client-written-cookies from the plan read) never block the deploy.