Stop two docstrings describing a schema that is gone

Pages and sections left in 7ff29ca. DashboardView still promised SectionDef
stayed and that the editor wrote back into the first section; the mosaic
still said "the first page's widgets". Comments only — the code was right.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01K1moruzue2kTJd3uVisgNk

frontend/src/components/Common/DashboardMosaic.tsx

@@ -65,10 +65,7 @@ type Block = {
   h: number
 }
 
-/**
- * The first page's widgets as one grid.
- *
- */
+/** The dashboard's widgets as one grid. */
 function blocksOf(dashboard: DashboardDef_Output): {
   blocks: Block[]
   rows: number

frontend/src/components/Dashboard/DashboardView.tsx

@@ -294,12 +294,12 @@ export const isPlaced = (widgets: WidgetDef[]) =>
   })
 
 /**
- * One page, drawn as the single grid the panel shows.
+ * A dashboard, drawn as the single grid the panel shows.
  *
  * A dashboard is one canvas — several dashboards on a panel is what the rail
- * is for — so the page's sections are one arrangement rather than a stack of
- * headed grids. `SectionDef` stays in the schema, and the editor writes what
- * it arranged back into the first section.
+ * is for — so its widgets are one arrangement rather than a stack of headed
+ * grids. Pages and sections left the schema in 7ff29ca; a document written
+ * the old way is flattened on read.
  */
 export function DashboardView({
   dashboard,