feat: queryAggregate() + HAVING, plus aggregate backfill, traversal depth/via, extraction typing (BR-ADV-FEATURES-BUN)

New report APIs:
- brain.queryAggregate(name, params) returns the clean AggregateResult[] shape
  ({ groupKey, metrics, count }) directly, instead of the search-Result wrapper that
  find({ aggregate }) returns.
- HAVING: find({ aggregate, having }) and queryAggregate filter groups by computed
  metric values (e.g. revenue > 1000), complementing where (which filters group keys).
  Evaluated per group: O(groups), independent of entity count.

Fixes (all reproducible on Node; surfaced under Cortex+Bun by Memory):
- Aggregate backfill-on-define: defining an aggregate over a store that already holds
  matching entities returned []. It now backfills from existing entities on first query
  (storage-agnostic via getNouns), so it works under durable backends that reopen
  pre-populated. groupBy:['noun'] resolves to the entity type; find({ aggregate }) rows
  expose groupKey/metrics/count at the top level.
- Multi-hop find({ connected: { depth, via } }) honors depth and via at every hop
  (was 1-hop only, with verb filtering applied to hop 1 only); BFS bounded by limit.
- extractEntities no longer bleeds a neighbour's type indicator across candidates; each
  candidate is typed by its own span. Also fixes the "Dr." title pattern.

Adds real-embedding regression tests; full unit suite green.

src/types/brainy.types.ts

@@ -783,6 +783,13 @@ export interface AggregateQueryParams {
   name: string
   /** Filter aggregate groups by their key values */
   where?: Record<string, unknown>
+  /**
+   * Filter groups by their computed METRIC values (SQL HAVING). Same BFO operators as
+   * `where`, but applied to the derived metric results plus `count`, e.g.
+   * `{ revenue: { greaterThan: 1000 } }`. Evaluated per group (O(groups), independent of
+   * entity count), before sort/pagination.
+   */
+  having?: Record<string, unknown>
   /** Sort by metric name or group key field */
   orderBy?: string
   /** Sort direction */