Profile per-column cardinality and extent; add data-aware chart warnings (M4, A3/A4)

src/core/dataset.ts

@@ -18,7 +18,7 @@
  */
 
 import type { DataFormat } from './format-detection';
-import { profileData, type DatasetProfile } from './profile';
+import { profileData, type ColumnStats, type DatasetProfile } from './profile';
 import type { ColumnType } from './type-inference';
 
 /** Current schema version for a Dataset record (read-time migration target). */
@@ -53,6 +53,8 @@ export interface Dataset {
   columns: string[];
   /** Per-column inferred type. */
   columnTypes: Array<{ name: string; type: ColumnType }>;
+  /** Per-column cardinality + numeric range (empty for URL / non-tabular). */
+  columnStats: ColumnStats[];
   /** Approximate payload size in bytes. */
   size: number;
   /** ISO timestamp — when first added. */
@@ -243,9 +245,10 @@ export interface CreateDatasetOptions {
 
 /**
  * Create a Dataset: stamps version/timestamps and runs `computeDatasetProfile` to
- * fill the derived summary fields. `id` defaults to `Date.now()` (numeric;
- * collision-prone for batch creation — see the DatasetStore.add TODO) and is
- * injectable for tests.
+ * fill the derived summary fields. `id` defaults to `Date.now()` (numeric) and is
+ * injectable for tests; note that `DatasetStore` is the id authority and reassigns
+ * a collision-free id on insertion (`nextDatasetId`), so this default never reaches
+ * storage through the normal create paths.
  */
 export function createDataset(options: CreateDatasetOptions): Dataset {
   const now = options.now ?? new Date();
@@ -264,6 +267,7 @@ export function createDataset(options: CreateDatasetOptions): Dataset {
     columnCount: profile.columnCount,
     columns: profile.columns,
     columnTypes: profile.columnTypes,
+    columnStats: profile.columnStats,
     size: profile.size,
     created: iso,
     modified: iso,