The docking engine was built correctly in v103.1.0 but had never run: it expects anchor.slot + mode:"docked", but all registry entries used anchor.offset and stored tiles had mode:undefined. Pure data/registry migration — no engine changes. Canvas tiles now dock.
v103.1.62026-06-03
·tileSectionRegistry: 6 canvas tiles converted to slot-anchors (right: physics/appearance/labels/typography; left: graph-sources/graph-inspector). 5 deferred sections left with offset anchors + deferred comment (they're mis-homed — belong in settings advanced-tabs)