Docs: move point-in-time records to exploration/, trim build-narration, lift open items to plan

docs/architecture/05-rendering-theming-preview.md

@@ -45,7 +45,7 @@ above it is data; everything below it is a Vega `View` we own and must tear down
 > the main Live Preview) reads runtime rows via `view.data(name)`. It rides this same
 > boundary: a `RenderHandle.data()` accessor wraps the view (like `toImageURL`), so no
 > component touches the raw view. Parked, not built — see
-> [`docs/data-inspector-exploration.md`](../data-inspector-exploration.md).
+> [`docs/exploration/data-inspector-exploration.md`](../exploration/data-inspector-exploration.md).
 
 ---
 
@@ -126,8 +126,7 @@ async function rerender(node: HTMLElement, spec: TopLevelSpec, config: Config) {
   crisp/inspectable/copyable and stays the default for the editor's LivePreview. But an
   SVG chart renders one DOM node per mark, so a many-mark chart (e.g. the Chart Builder's
   default one-bar-per-row on a 10k-row dataset) costs **seconds** of main-thread
-  layout/paint per render (measured ~6.5s on 9994 rows; the chart paints _after_ it first
-  appears, freezing the tab). The **Chart Builder preview** therefore passes
+  layout/paint per render (the chart paints _after_ it first appears, freezing the tab). The **Chart Builder preview** therefore passes
   `renderSpec(…, { renderer: 'canvas' })` — canvas is a single node and paints in
   milliseconds. The raster trade-off is invisible for an ephemeral preview, and image
   export (`view.toImageURL`) is renderer-agnostic.
@@ -165,7 +164,7 @@ background, the categorical color range. Astrolabe ships one config per UI theme
 so charts visually belong to the app rather than looking like stock Vega-Lite.
 `src/core/vega-themes.ts` is the single source of truth; each house config is
 **two merged layers** (the full audit and forward plan live in
-[`docs/chart-theming-scope.md`](../chart-theming-scope.md)):
+[`docs/exploration/chart-theming-scope.md`](../exploration/chart-theming-scope.md)):
 
 - **Base** (`lightBaseConfig`/`darkBaseConfig`) — the legibility minimum:
   `background: 'transparent'` (the pane shows through) plus guide colors on the