Builds are coordinated by nodes, not by lease files

Deciding who compiles the platform's dynamic content used to happen outside the mesh — in a lease file on a shared volume that nothing could observe, query, or reason about. When coordination went wrong, it went wrong invisibly.

Build coordination is now mesh state. A durable build root records who currently builds (candidates register, and the node's own arbiter grants the earliest request — a builder that dies is superseded automatically), and a per-version history of completed builds that never forgets: finishing a new build cannot revoke an older one's record, so servers on the previous version are never destabilised by a rollout in progress.

Named chunks — each defined by ordinary mesh queries, as simple as a list of paths or a whole module — get their own build nodes under the root, each with its claim, its pinned source commits, and the release paths it produced. That makes a build observable like any other content: you can see what is building, what is done, and exactly what each part wrote.

Nothing executes against it yet — this protocol is the coordination layer that chunked build execution and version-aware readiness plug into next.