Check both #file-absolute and CWD-relative paths for the PipelineHelpers sibling

The sibling-checkout check (use ../PipelineHelpers when building from
the umbrella monorepo, else fall back to GitHub) compared against a CWD-
relative path, which isn't always the manifest's own directory (Xcode
workspace builds, e.g.). Resolving purely from #file isn't a strict fix
either -- a cached manifest could have a stale baked-in #file from a
previous checkout location -- so this checks both the #file-derived
absolute path and the original CWD-relative path, succeeding if either
finds the sibling.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>

Author: dsward2

Package.swift

@@ -4,10 +4,18 @@ import Foundation
 
 // Use the local PipelineHelpers sibling when building from the umbrella monorepo;
 // fall back to GitHub when used standalone.
-let pipelineHelpersDep: Package.Dependency = FileManager.default.fileExists(
-    atPath: "../PipelineHelpers/Package.swift"
-) ? .package(path: "../PipelineHelpers")
-  : .package(url: "https://github.com/dsward2/PipelineHelpers", branch: "main")
+// Check via both #file (absolute, compile-time) and CWD-relative (runtime) paths so
+// the sibling is found in all contexts: direct SwiftPM invocations, Xcode workspace
+// builds, and standalone Package.swift opens where a cached manifest might have a
+// stale baked-in #file from a previous location.
+let _manifestDir = URL(fileURLWithPath: #file).deletingLastPathComponent()
+let _siblingAbsPath = _manifestDir.appendingPathComponent("../PipelineHelpers/Package.swift").standardized.path
+let _siblingRelPath = "../PipelineHelpers/Package.swift"
+let _hasSibling = FileManager.default.fileExists(atPath: _siblingAbsPath)
+                   || FileManager.default.fileExists(atPath: _siblingRelPath)
+let pipelineHelpersDep: Package.Dependency = _hasSibling
+    ? .package(path: "../PipelineHelpers")
+    : .package(url: "https://github.com/dsward2/PipelineHelpers", branch: "main")
 
 let package = Package(
     name: "LiveAudioServer",