fix(eval): teardown PGLite engines so bun run eval:run exits 0

The multi-adapter runner left PGLite engines alive after each run.
GbrainAfterAdapter and HybridNoGraphAdapter both instantiate a
PGLiteEngine in init() but never disconnect it; Bun's shutdown path
exits with code 99 when embedded-Postgres workers outlive main().

Added optional `teardown?(state)` to the Adapter interface, implemented
it on both engine-backed adapters, and call it from scoreOneRun after
the N=5 loop. ripgrep-bm25 and vector-only hold no DB resources and
don't need a teardown.

Verified: gbrain-after, hybrid-nograph, ripgrep-bm25, vector-only all
exit 0 at N=1. Full test:eval passes (57 tests). No metric change.

eval/runner/adapters/hybrid-nograph.ts

@@ -76,6 +76,11 @@ export class HybridNoGraphAdapter implements Adapter {
     return { engine } satisfies HybridNoGraphState;
   }
 
+  async teardown(state: BrainState): Promise<void> {
+    const s = state as HybridNoGraphState;
+    await s.engine.disconnect();
+  }
+
   /** Build a markdown string importFromContent can parse.
    *  Format: YAML frontmatter then body; matches what gbrain import expects. */
   private buildContentMarkdown(p: Page): string {

eval/runner/multi-adapter.ts

@@ -217,6 +217,11 @@ class GbrainAfterAdapter implements Adapter {
       rank: i + 1,
     }));
   }
+
+  async teardown(state: unknown): Promise<void> {
+    const { engine } = state as { engine: PGLiteEngine };
+    await engine.disconnect();
+  }
 }
 
 /**
@@ -340,6 +345,7 @@ async function scoreOneRun(
     for (const r of topK) if (relevant.has(r.page_id)) totalCorrect++;
     totalExpected += relevant.size;
   }
+  if (adapter.teardown) await adapter.teardown(state);
   return {
     mean_precision_at_k: queries.length > 0 ? totalP / queries.length : 0,
     mean_recall_at_k: queries.length > 0 ? totalR / queries.length : 0,

eval/runner/types.ts

@@ -179,6 +179,14 @@ export interface Adapter {
    * Adapters that don't have a poison path return an empty map.
    */
   getPoisonDisposition?(state: BrainState): Record<string, PoisonDisposition>;
+
+  /**
+   * Release any resources held by `state` (DB connections, file locks,
+   * worker threads). Called once per run after scoring completes.
+   * Adapters that hold no resources can omit this. Without it, PGLite-backed
+   * adapters leak engine workers and Bun exits 99 at the end of the run.
+   */
+  teardown?(state: BrainState): Promise<void>;
 }
 
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