Six bite-sized tasks for spec 0037: aura-core records a BoundParam (original slot
position) in bind + a bound_params() accessor; aura-engine emits a conditional
"bound" field via scalar_str; graph-viewer.js merges free+bound params into slot
order and renders the bound slot dimmed as name=value; re-capture the sample-model
fixture; a new headless render guard (trailing + middle bind); full-workspace gate.
refs #63
