Fix busy-wait polling in CheckpointReactor tests

Replace Effect.yieldNow (near-instant microtask resolution) with
Effect.sleep("10 millis") to restore a real delay between poll
iterations in waitForThread, waitForEvent, and waitForGitRefExists.

Without a real delay, these polling loops spin as tight busy-waits,
starving the event loop of time to process I/O callbacks from git
operations and database writes.

Author: cursoragent

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

@@ -170,7 +170,7 @@ async function waitForThread(
     if ((await Effect.runPromise(Clock.currentTimeMillis)) >= deadline) {
       throw new Error("Timed out waiting for thread state.");
     }
-    await Effect.runPromise(Effect.yieldNow);
+    await Effect.runPromise(Effect.sleep("10 millis"));
     return poll();
   };
   return poll();
@@ -192,7 +192,7 @@ async function waitForEvent(
     if ((await Effect.runPromise(Clock.currentTimeMillis)) >= deadline) {
       throw new Error("Timed out waiting for orchestration event.");
     }
-    await Effect.runPromise(Effect.yieldNow);
+    await Effect.runPromise(Effect.sleep("10 millis"));
     return poll();
   };
   return poll();
@@ -239,7 +239,7 @@ async function waitForGitRefExists(cwd: string, ref: string, timeoutMs = 15_000)
     if ((await Effect.runPromise(Clock.currentTimeMillis)) >= deadline) {
       throw new Error(`Timed out waiting for git ref '${ref}'.`);
     }
-    await Effect.runPromise(Effect.yieldNow);
+    await Effect.runPromise(Effect.sleep("10 millis"));
     return poll();
   };
   return poll();