fix(server): let stopped threads settle immediately (#5553)

Author: t3dotgg

apps/server/src/orchestration/Layers/ProjectionPipeline.test.ts

@@ -1430,6 +1430,13 @@ it.layer(BaseTestLayer)("OrchestrationProjectionPipeline", (it) => {
       assert.deepEqual(settledRows, [
         { state: "completed", completedAt: "2026-01-01T00:01:00.000Z" },
       ]);
+
+      const threadRows = yield* sql<{ readonly latestTurnId: string | null }>`
+        SELECT latest_turn_id AS "latestTurnId"
+        FROM projection_threads
+        WHERE thread_id = ${threadId}
+      `;
+      assert.deepEqual(threadRows, [{ latestTurnId: turnId }]);
     }),
   );
 

apps/server/src/orchestration/Layers/ProjectionPipeline.ts

@@ -850,7 +850,8 @@ const makeOrchestrationProjectionPipeline = Effect.fn("makeOrchestrationProjecti
           }
           yield* projectionThreadRepository.upsert({
             ...existingRow.value,
-            latestTurnId: event.payload.session.activeTurnId,
+            // activeTurnId describes current work; a terminal session must not erase history.
+            latestTurnId: event.payload.session.activeTurnId ?? existingRow.value.latestTurnId,
             updatedAt: event.occurredAt,
           });
           yield* refreshThreadShellSummary(event.payload.threadId);