feat(namespace): aggregation reads under the law + epoch 3 (the key-split rebuild) + THE ARMING COMMIT — the capability constant, the law module, and the typed refusals export from the package root; both engines' conformance suites light on this signal

src/brainy.ts

@@ -5619,7 +5619,7 @@ export class Brainy<T = any> implements BrainyInterface<T> {
       this._aggregationIndex!.defineAggregate({
         name: aggregateName,
         source: {},
-        groupBy: perType ? [name, 'noun'] : [name],
+        groupBy: perType ? [name, 'system.type'] : [name],
         metrics: { count: { op: 'count' } }
       })
     }
@@ -5630,7 +5630,12 @@ export class Brainy<T = any> implements BrainyInterface<T> {
    * and `counts.byField()` agree on the convention.
    */
   private fieldCountsAggregateName(name: string): string {
-    return `__fieldCounts__${name}`
+    // v2 suffix: the per-type dimension moved from the legacy 'noun' alias to
+    // 'system.type' under the addressing law — a NEW name makes the ensure
+    // block re-define and BACKFILL from canonical instead of silently serving
+    // the old-dim definition (whose 'noun' key now reads user metadata and
+    // would drift). The v1 rows are derived state, superseded not lost.
+    return `__fieldCounts_v2__${name}`
   }
 
   /**
@@ -11852,7 +11857,7 @@ export class Brainy<T = any> implements BrainyInterface<T> {
           // don't have the tracked field at all (e.g. the VFS root) bucket under
           // '__null__' and would otherwise pollute the count map.
           if (value === undefined || value === null || value === '__null__') continue
-          if (options?.type !== undefined && row.groupKey?.['noun'] !== options.type) continue
+          if (options?.type !== undefined && row.groupKey?.['system.type'] !== options.type) continue
           const key = String(value)
           result[key] = (result[key] || 0) + (typeof row.metrics?.count === 'number' ? row.metrics.count : row.count)
         }