fix: fail fast on missing host IPC dir for task runtimes

runners/agent-runner/src/ipc-paths.ts

@@ -0,0 +1,29 @@
+import path from 'path';
+
+export interface ResolvedIpcDirectories {
+  ipcDir: string;
+  hostIpcDir: string;
+}
+
+export function isTaskScopedIpcDir(ipcDir: string): boolean {
+  const normalized = path.posix.normalize(ipcDir.replaceAll('\\', '/'));
+  return /\/tasks\/[^/]+\/?$/.test(normalized);
+}
+
+export function resolveIpcDirectories(
+  env: NodeJS.ProcessEnv,
+): ResolvedIpcDirectories {
+  const ipcDir = env.EJCLAW_IPC_DIR || '/workspace/ipc';
+  const hostIpcDir = env.EJCLAW_HOST_IPC_DIR;
+
+  if (!hostIpcDir && isTaskScopedIpcDir(ipcDir)) {
+    throw new Error(
+      'EJCLAW_HOST_IPC_DIR is required for task-scoped IPC runtimes',
+    );
+  }
+
+  return {
+    ipcDir,
+    hostIpcDir: hostIpcDir || ipcDir,
+  };
+}