test(graph): cut graphIndex-pagination from 304s to under a second

18 pagination tests recreated a fresh FileSystemStorage-backed Brainy plus
51 real-embedded entities (1 central hub + 50 neighbors) in a beforeEach
before EVERY test — ~950 add()/relate() calls total, each paying the real
ONNX embedder. Measured before this change: 303.69s (fresh run, this
session). None of these tests exercise similarity search, only graph
pagination, so three changes cut the cost without touching an assertion:

- vector: [] on every add() — add()'s `params.vector || embed(...)` never
  calls the embedder once vector is present, even the sanctioned unvectored
  [] shape (confirmed against brainy.ts's zero-norm-law comment: the
  dimension-pinning gate is `vector.length > 0`, so [] never poisons
  dimensions for a later real embed).
- storage: { type: 'memory' } instead of the 'auto' default (FileSystemStorage
  at ./brainy-data) — sidesteps tests/setup.ts's global per-test
  `rm -rf brainy-data`, which would otherwise corrupt a brain shared across
  a describe's beforeAll out from under it.
- the base fixture (hub + 50 neighbors) now builds once per describe
  (beforeAll) instead of once per test — safe because no test in a given
  describe mutates the shared fixture in a way an earlier sibling test's
  assertion depends on (the one mutating case is the last test in its
  describe).

Measured after: 416ms for all 18 tests (2.35s wall including vitest
startup), all 18 still passing.

tests/integration/graphIndex-pagination.test.ts

@@ -9,9 +9,34 @@
  * 8.0 BigInt boundary: entity ints in (resolved via the metadata index's
  * idMapper), entity/verb ints out (`bigint[]`). Entity ints map back to UUIDs
  * via `idMapper.getUuid(Number(int))`; verb ints via `verbIntsToIds()`.
+ *
+ * COST NOTE (2026-09): this file's `beforeEach` used to recreate a fresh
+ * FileSystemStorage-backed Brainy plus 51 real-embedded entities before
+ * EVERY one of the 18 tests below (~950 add()/relate() calls total, each
+ * paying the real ONNX embedder — the whole file walled ~328s). Fixed
+ * without touching a single assertion:
+ *
+ * (1) `vector: []` on every add() below — these tests exercise graph
+ *     pagination, never similarity, so a pre-supplied vector is honest, not
+ *     a shortcut: `add()`'s `params.vector || (await this.embed(...))` never
+ *     calls the embedder once `vector` is present, even the sanctioned
+ *     unvectored `[]` shape (see brainy.ts's add(), the zero-norm-law
+ *     comment) — and the `vector.length > 0` gate on dimension-pinning means
+ *     `[]` never poisons `this.dimensions` for later real embeds.
+ * (2) `storage: { type: 'memory' }` instead of the 'auto' default
+ *     (FileSystemStorage at ./brainy-data) — real disk I/O the pagination
+ *     assertions never needed, and it sidesteps tests/setup.ts's global
+ *     per-test `rm -rf brainy-data`, which would otherwise corrupt a brain
+ *     shared across a describe's beforeAll out from under it.
+ * (3) the base fixture (one central hub + 50 outgoing-edge neighbors) now
+ *     builds ONCE per describe (`beforeAll`) instead of once per test — safe
+ *     because no test in a given describe block mutates the shared fixture
+ *     in a way an earlier sibling test's assertion depends on (the one
+ *     mutating case, the incoming-direction test, is the LAST test in its
+ *     describe).
  */
 
-import { describe, it, expect, beforeEach } from 'vitest'
+import { describe, it, expect, beforeAll, afterAll } from 'vitest'
 import { Brainy } from '../../src/brainy.js'
 import { NounType, VerbType } from '../../src/types/graphTypes.js'
 
@@ -39,14 +64,21 @@ describe('GraphAdjacencyIndex Pagination', () => {
       .map((i) => idMapper().getUuid(Number(i)))
       .filter((u: string | undefined): u is string => u !== undefined)
 
-  beforeEach(async () => {
+  /**
+   * Builds one central hub + 50 neighbor entities (all outgoing edges from
+   * the hub), unvectored and on in-memory storage (see the file header).
+   * Assigns the describe-scoped `brain`/`centralId`/`neighborIds` above;
+   * called once per describe via `beforeAll`, not once per test.
+   */
+  async function buildFixture(): Promise<void> {
     brain = new Brainy({ requireSubtype: false })
-    await brain.init()
+    await brain.init({ storage: { type: 'memory' } })
 
     // Create central entity
     centralId = await brain.add({
       data: { name: 'Central Hub' },
-      type: NounType.Thing
+      type: NounType.Thing,
+      vector: []
     })
 
     // Create 50 neighbor entities with relationships
@@ -54,7 +86,8 @@ describe('GraphAdjacencyIndex Pagination', () => {
     for (let i = 0; i < 50; i++) {
       const neighborId = await brain.add({
         data: { name: `Neighbor ${i}`, index: i },
-        type: NounType.Thing
+        type: NounType.Thing,
+        vector: []
       })
       neighborIds.push(neighborId)
 
@@ -65,9 +98,14 @@ describe('GraphAdjacencyIndex Pagination', () => {
         type: VerbType.RelatesTo
       })
     }
-  })
+  }
 
   describe('getNeighbors() Pagination', () => {
+    beforeAll(buildFixture)
+    afterAll(async () => {
+      await brain?.close()
+    })
+
     it('should return all neighbors without pagination', async () => {
       const neighborInts = await graphIndex().getNeighbors(entityInt(centralId))
       const neighbors = intsToUuids(neighborInts)
@@ -149,7 +187,8 @@ describe('GraphAdjacencyIndex Pagination', () => {
       // Create some incoming relationships
       const sourceId = await brain.add({
         data: { name: 'Source' },
-        type: NounType.Thing
+        type: NounType.Thing,
+        vector: []
       })
 
       await brain.relate({
@@ -169,6 +208,11 @@ describe('GraphAdjacencyIndex Pagination', () => {
   })
 
   describe('getVerbIdsBySource() Pagination', () => {
+    beforeAll(buildFixture)
+    afterAll(async () => {
+      await brain?.close()
+    })
+
     it('should return all verb ints without pagination and resolve them back to ids', async () => {
       const verbInts: bigint[] = await graphIndex().getVerbIdsBySource(entityInt(centralId))
 
@@ -223,6 +267,11 @@ describe('GraphAdjacencyIndex Pagination', () => {
   })
 
   describe('getVerbIdsByTarget() Pagination', () => {
+    beforeAll(buildFixture)
+    afterAll(async () => {
+      await brain?.close()
+    })
+
     it('should return all verb ints targeting an entity', async () => {
       // Pick a neighbor that's a target of relationships
       const targetId = neighborIds[0]
@@ -236,14 +285,16 @@ describe('GraphAdjacencyIndex Pagination', () => {
       // Create entity with many incoming relationships
       const popularTarget = await brain.add({
         data: { name: 'Popular Target' },
-        type: NounType.Thing
+        type: NounType.Thing,
+        vector: []
       })
 
       // Create 30 relationships pointing to it
       for (let i = 0; i < 30; i++) {
         const sourceId = await brain.add({
           data: { name: `Source ${i}` },
-          type: NounType.Thing
+          type: NounType.Thing,
+          vector: []
         })
         await brain.relate({
           from: sourceId,
@@ -267,6 +318,11 @@ describe('GraphAdjacencyIndex Pagination', () => {
   })
 
   describe('Performance with Pagination', () => {
+    beforeAll(buildFixture)
+    afterAll(async () => {
+      await brain?.close()
+    })
+
     it('should maintain sub-5ms performance with pagination', async () => {
       const central = entityInt(centralId)
 
@@ -285,11 +341,17 @@ describe('GraphAdjacencyIndex Pagination', () => {
   })
 
   describe('Real-World Use Cases', () => {
+    beforeAll(buildFixture)
+    afterAll(async () => {
+      await brain?.close()
+    })
+
     it('should efficiently paginate through high-degree node', async () => {
       // Simulate popular entity with 100+ relationships
       const hub = await brain.add({
         data: { name: 'Popular Hub' },
-        type: NounType.Thing
+        type: NounType.Thing,
+        vector: []
       })
 
       // Create 100 relationships
@@ -297,7 +359,8 @@ describe('GraphAdjacencyIndex Pagination', () => {
       for (let i = 0; i < 100; i++) {
         const targetId = await brain.add({
           data: { name: `Target ${i}` },
-          type: NounType.Thing
+          type: NounType.Thing,
+          vector: []
         })
         targetIds.push(targetId)
         await brain.relate({