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/db/fieldAddressing.ts

@@ -283,3 +283,11 @@ export class UnsupportedFindOptionError extends Error {
     this.option = option
   }
 }
+
+/**
+ * @description The capability signal both engines' conformance suites arm on
+ * (never a version guess): its presence at the package root means the one
+ * field-addressing law is LIVE on every query surface — bare = user metadata,
+ * `system.*` = the ruled scalars, plumbing invisible, refusals typed.
+ */
+export const FIELD_ADDRESSING_CAPABILITY = 'field-addressing/v1'