fix(library): preserve folder creation order

Keep unrelated folder selections in the order users add them, and make API reads deterministic so web and iOS defaults use the same first folder.

Fixes #1412

client/src/features/library/composables/__tests__/folder-paths.spec.ts

@@ -11,6 +11,10 @@ describe('folder path selection', () => {
     expect(consolidateFolderPaths(['/books/fiction', '/audio', '/books', '/books/fantasy'])).toEqual(['/audio', '/books'])
   })
 
+  it('preserves the order of unrelated folders', () => {
+    expect(consolidateFolderPaths(['/library/zz', '/library/alpha-long', '/library/m'])).toEqual(['/library/zz', '/library/alpha-long', '/library/m'])
+  })
+
   it('finds the selected path that already covers a nested folder', () => {
     expect(coveringFolderPath('/books/fiction/scifi', ['/books', '/books/fiction'])).toBe('/books/fiction')
   })

client/src/features/library/composables/folder-paths.ts

@@ -15,8 +15,8 @@ export function coveringFolderPath(path: string, candidates: string[]): string |
 }
 
 export function consolidateFolderPaths(paths: string[]): string[] {
-  const unique = [...new Set(paths.map(normalizeFolderPath))].sort((a, b) => a.length - b.length || a.localeCompare(b))
-  return unique.filter((path, index) => !unique.slice(0, index).some((candidate) => isPathInside(path, candidate)))
+  const unique = [...new Set(paths.map(normalizeFolderPath))]
+  return unique.filter((path) => !unique.some((candidate) => candidate !== path && isPathInside(path, candidate)))
 }
 
 function isPathInside(path: string, parent: string): boolean {