Construct swimlanes from measured geometry

[ivanmkc]

Summary

• construct horizontal and vertical swimlanes from painted node/group/edge-label measurements
• enforce shared lane length, standard 24px parent gaps, 32px member separation, and measured label strips
• route every edge from explicit face-center anchors, reserving exterior measured-label channels when needed
• atomically reveal the result and open long LR/default-direction journeys at their start
• make visible render errors fail the gallery harness and shrink the overlap ledger to empty

Visual evidence

Before (gallery baseline):

After (this branch, start-anchored):

Verification

• full workspace suite: 1,064 passed, 18 skipped
• strict gallery sweep, twice-rendered per board: 32/32 clean, 0 known-bad, 0 regressions; render errors now fail rather than masquerade as zero-node passes
• dedicated commerce swimlane contract repeated: no node/container overlap, no spillout, standard padding/gaps, exact anchors, visible label, no edge-over-node crossing
• explicit LR and omitted-direction LR-default viewport-start checks: 44px opening inset
• data-lineage, ETL, infrastructure, Kubernetes, architecture tiers, support escalation, full and synthetic swimlanes all render clean
• viewer production build

Stack

Depends on #307, which depends on #306, which depends on #305.