A layer is one plotting space with several marks stacked in z-order, so it now renders as a single frame holding its child marks as a row of glyphs, badged with a new 'layers' glyph — instead of offset stacked cards that read as separate spaces and hid the lower glyphs. Each mark stays an individual treeitem, so selection and Alt+up/down z-order reorder are unchanged.
Drag a view's box (or Alt+up/down) to reorder it within its container; drag onto another view's edge to pair the two in a new row/column, move across containers, or insert. Each leaf shows a glyph of its mark type.
Core: spec-restructure.wrapViews (wrap, with flatten-to-insert, collapse, and data-pin invariants) and spec-insert.moveViewTo; the editor applies every drag as one undoable edit via AppStore.composeRequest, keeping the editor the single text source.
A collapsible Data panel under the Live Preview and Chart Builder charts shows the rows the chart actually uses, switching between Input (parsed source) and Resolved (post-transform) views read from the live Vega view. Collapsed by default; the open-state and a draggable height divider persist.
Rows come through a new RenderHandle.inspectData() accessor, so no component touches the view: core/result-data picks the most-upstream source and most-downstream result from the compiled dataflow, read lazily. The divider reuses the window-splitter pattern (horizontal variant).
Consolidations: a shared DataTable primitive replaces the inspector's and the builder's duplicate read-only tables; useResizeDrag merges the col/row drag-gesture twins.
Docs: spec 04/06 and arch 05/10 updated; the now-shipped exploration memo removed.
Multi-page Vite build: index.html serves a new standalone landing
(src/landing), app/index.html serves the app at /app/. The PWA service
worker and manifest are scoped to /app/, so the landing stays
uncontrolled and always-fresh; hash view-state routing is unchanged.
The landing reuses src/core and the chart-renderer service only (never
stores/orchestration/modals/components) and lazy-loads Vega. Its demos
drive the real core: a hero snippet switcher over CHART_EXAMPLES, an
interactive Chart Builder over a new profiled core fixture
(sample-dataset), and a Theme Builder gallery with three from-scratch
custom themes plus built-in presets.