Keep builds in the builds bucket and move the build rows there at start (issue 1090)

Once chain_moved records the kind, RecordBuild and every build read go through the chain (reuse key and published added); before that the tables are read as before. The serving controller copies the rows at its start, holding the lease: idempotent per key, rows counted against keys, the largest value measured, a refusal (urgent condition, nothing switched) on a count that differs or a value over the bus's largest, and a re-read when the table took a row meanwhile. ForTest attaches the chain in memory with builds moved; ForTestBefore leaves it unmoved. Build requests, gates and the other kinds are still in their tables.

cmd/mesh-controller/push.go

@@ -172,6 +172,11 @@ func serve(ctx context.Context) (err error) {
 		return err
 	}
 	defer server.Close()
+	// The chain on the bus, and the move of what the tables still hold into it (novox/hq ADR 0408 §8): before anything
+	// reads builds, rollouts or assignments.
+	if err := attachTheChain(ctx, inv, server); err != nil {
+		return err
+	}
 
 	// The bus's own objects, asserted on every start. **Not created once at genesis**: a stream
 	// somebody deleted, a mesh raised from a restored backup, or a bus whose data directory was