Fix worker error cleanup and skip subprocess polling when idle

- CoalescingDrainableWorker: Add Effect.onError handler to remove key from
  activeKeys when process fails, preventing drainKey/drain from hanging forever

- Terminal Manager: Skip subprocess polling when no running sessions exist,
  avoiding unnecessary subprocess checker invocations during idle periods

Author: cursoragent

apps/server/src/terminal/Layers/Manager.ts

@@ -1377,6 +1377,10 @@ export const makeTerminalManagerWithOptions = Effect.fn("makeTerminalManagerWith
           session.status === "running" && Number.isInteger(session.pid),
       );
 
+      if (runningSessions.length === 0) {
+        return;
+      }
+
       yield* Effect.forEach(
         runningSessions,
         (session) =>
@@ -1434,8 +1438,20 @@ export const makeTerminalManagerWithOptions = Effect.fn("makeTerminalManagerWith
       );
     });
 
+    const hasRunningSessions = readManagerState.pipe(
+      Effect.map((state) => [...state.sessions.values()].some((s) => s.status === "running")),
+    );
+
     yield* Effect.forever(
-      Effect.sleep(subprocessPollIntervalMs).pipe(Effect.flatMap(() => pollSubprocessActivity())),
+      hasRunningSessions.pipe(
+        Effect.flatMap((active) =>
+          active
+            ? pollSubprocessActivity().pipe(
+                Effect.flatMap(() => Effect.sleep(subprocessPollIntervalMs)),
+              )
+            : Effect.sleep(subprocessPollIntervalMs),
+        ),
+      ),
     ).pipe(Effect.forkIn(workerScope));
 
     yield* Effect.addFinalizer(() =>

packages/shared/src/CoalescingDrainableWorker.ts

@@ -77,7 +77,17 @@ export const makeCoalescingDrainableWorker = <K, V, E, R>(options: {
           ] as const;
         }).pipe(Effect.tx),
       ),
-      Effect.flatMap((item) => (item === null ? Effect.void : processKey(item.key, item.value))),
+      Effect.flatMap((item) =>
+        item === null
+          ? Effect.void
+          : Effect.onError(processKey(item.key, item.value), () =>
+              TxRef.update(stateRef, (state) => {
+                const activeKeys = new Set(state.activeKeys);
+                activeKeys.delete(item.key);
+                return { ...state, activeKeys };
+              }),
+            ),
+      ),
       Effect.forever,
       Effect.forkScoped,
     );