Unit 4 of the sound-bar refactor. `Controls/AudioDock` takes the bottom row that held the empty
`BottomBar` spacer (deleted): four bay containers (MIC / GAME / TRAX / LIP-SYNC) above a 36px
master strip, all token-styled.
Height comes from `Models/AudioDockLayout`, not from a setting: 168px normally, 36px below a 900px
window height. At the 1366×768 minimum a full dock leaves ~398px for the preview, so the collapse
is mandatory, not cosmetic. The dock listens to its window's SizeChanged and re-applies.
Nothing here pretends to be a meter yet — the bays and the master readouts fill in over the next
units, each with its own test.
Guard: AudioDockLayoutTests pins both sides of the threshold (768 collapsed, 1040 expanded), the
boundary itself, and the two heights as the design's numbers.
