Review round 2: change A must not slow builds before any slice exists, so a
module given no share sets no GOMAXPROCS. The slice's quota bounds the total;
threads only size one step, from the node's share over the module's own
capacity (shanks: 24 x 50% / 3 = 4). The share is the node-engine's own config.
Review round 1: the decoder type ships before any composer can emit it, so a
routine SDK bump never sends yields to an engine that refuses them; the
composer half moves to a later change. Every yielding process of a node goes
into one top-level slice, meshyield.slice, so the three build modules share one
quota instead of taking one each; the share is one node value, node-tools'
build-cpu-share, and each step's threads divide it by every build slot of the
node (words from the composer, a conservative fallback without them).
The operator's desktop slows while it builds: the Go build runtime took 1650% of
shanks' 24 processors with nothing holding it back. A build seat's holder now
runs its runtime at idle priority under its node's cpu-cap share (declaration
Yields, composed from Seat.Yields and the module's cpu-cap setting), and
buildcpu/buildstep give each step its part of that cap in threads.
jschoubben