test(8.0): cover pending-tier range queries + setRetentionBudget adaptive reclaim

Closes the two coverage gaps a temporal-completeness audit surfaced (the code
was already correct, just untested):
- changedBetween / generationsTouching include un-flushed PENDING generations
  and stay identical across the flush — the building blocks of since/diff/history
  see single-op writes with no forced flush.
- setRetentionBudget() drives adaptive auto-compaction on flush() down to the
  byte budget: history is reclaimed, the live record is untouched (the cor #65
  retention-consume wiring, proven end-to-end).

65 generation/temporal tests green; 1528 unit green.

tests/integration/db-mvcc.test.ts

@@ -1240,6 +1240,26 @@ describe('8.0 Db API — generational MVCC', () => {
     await expect(reopened.asOf(1)).rejects.toBeInstanceOf(GenerationCompactedError)
   })
 
+  it('Model-B retention — setRetentionBudget drives adaptive reclaim on flush; live data intact', async () => {
+    // Default brain → ADAPTIVE retention. A coordinator (e.g. cor's ResourceManager)
+    // pushes a byte budget via setRetentionBudget(); auto-compaction on flush() reclaims
+    // oldest history down toward it. Each update's before-image carries the full prior
+    // 384-dim vector (~KBs), so ~13 generations far exceed a few-KB budget.
+    const { brain } = await openFsBrain()
+    const a = uid('ret-budget')
+    await brain.add({ id: a, type: NounType.Document, data: 'v0', vector: vec(1), metadata: { v: 0 } })
+    for (let v = 1; v <= 12; v++) await brain.update({ id: a, metadata: { v } })
+
+    brain.setRetentionBudget(6000) // ~6 KB — well below the accumulated history
+    await brain.flush() // group-commit + adaptive auto-compaction under the budget
+
+    // History was reclaimed (the horizon advanced past the oldest generations)…
+    expect(generationStoreOf(brain).horizon()).toBeGreaterThan(0)
+    await expect(brain.asOf(1)).rejects.toBeInstanceOf(GenerationCompactedError)
+    // …but the budget reclaims HISTORY only — the live record is untouched.
+    expect((await brain.get(a))?.metadata?.v).toBe(12)
+  })
+
   // ==========================================================================
   // 9. asOf() / released-Db error paths (Y.15 spot-checks)
   // ==========================================================================

tests/unit/db/generationStore.test.ts

@@ -363,6 +363,24 @@ describe('db/GenerationStore', () => {
       expect(store.hasCommittedAfter(g1)).toBe(true)
     })
 
+    it('range queries (changedBetween / generationsTouching) include un-flushed pending generations', async () => {
+      // Two single-op writes to different ids, NEITHER flushed (still in the
+      // pending tier). diff()/since()/history() are built on these, so they must
+      // see un-flushed single-ops with NO forced flush.
+      const g1 = await singleOpWrite(ID_A, 1)
+      const g2 = await singleOpWrite(ID_B, 1)
+      expect(store.committedGeneration()).toBe(0) // nothing on disk yet
+
+      const changed = await store.changedBetween(0, store.generation())
+      expect(changed.nouns).toEqual([ID_A, ID_B]) // resolves over committed ∪ pending
+      expect(await store.generationsTouching('noun', ID_A, 0, store.generation())).toEqual([g1])
+      expect(await store.generationsTouching('noun', ID_B, 0, store.generation())).toEqual([g2])
+
+      // …and the range stays identical across the flush (now reading from disk).
+      await store.flushPendingSingleOps()
+      expect((await store.changedBetween(0, store.generation())).nouns).toEqual([ID_A, ID_B])
+    })
+
     it('flush persists pending single-op generations (groupCommit-marked) and advances committed', async () => {
       await singleOpWrite(ID_A, 1)
       await singleOpWrite(ID_A, 2)