Pure structural seam — no layout changes yet (B3 wires the page through).
apps/app/src/lib/timetable/row-height.ts (NEW):
computeStageRowHeight(laneCount, laneHeightPx, lanePadPx) — one-line pure
function with the existing math: max(1, laneCount) * (laneHeight + lanePad) + lanePad.
Math.max(1, laneCount) keeps an empty stage row visible at single-lane
height instead of collapsing.
apps/app/src/components/timetable/StageRow.vue:
Switches its inline rowHeightPx computation to call the helper. Behavior
identical (the math was the helper's body).
apps/app/src/components/timetable/StageHeaderCell.vue:
New optional `rowHeightPx?: number` prop. When provided (B3 will pass it
from the page via the same helper), the header root applies blockSize
inline so the sticky-left column aligns pixel-for-pixel with the row.
When omitted, the legacy `block-size: 100%` CSS still applies — every
existing call-site keeps working.
apps/app/src/lib/timetable/index.ts: re-export the new helper.
Tests still green (389 across 54 files); typecheck clean.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
bert.hausmans
4d2282f546