fix(mobile): natural sort in the mobile file explorer

Mobile re-sorted host readDir results with bare localeCompare, undoing
the host funnel's natural order (round-2 review). Reuse the shared
comparator and pin the order in the mobile suite.

mobile/src/files/file-tree.test.ts

@@ -34,6 +34,18 @@ describe('file-tree', () => {
     ])
   })
 
+  it('orders numbered names naturally, matching the desktop explorer', () => {
+    const cache: DirectoryCache = {
+      '': { entries: [entry('100 - b.txt'), entry('9 - c.txt'), entry('99 - a.txt')] }
+    }
+
+    expect(flattenDirectoryCache(cache, new Set()).map((row) => row.id)).toEqual([
+      'file:9 - c.txt',
+      'file:99 - a.txt',
+      'file:100 - b.txt'
+    ])
+  })
+
   it('mirrors desktop default browse exclusions while keeping dotfiles visible', () => {
     const cache: DirectoryCache = {
       '': {

mobile/src/files/file-tree.ts

@@ -1,5 +1,6 @@
 // Pure tree projection for the mobile file explorer. Mobile mirrors desktop
 // browse semantics by flattening cached files.readDir results as folders open.
+import { compareFileNames } from '../../../src/shared/file-name-sort'
 
 export type MobileDirEntry = {
   name: string
@@ -118,7 +119,7 @@ function compareDirectoryEntries(a: MobileDirEntry, b: MobileDirEntry): number {
   if (a.isDirectory !== b.isDirectory) {
     return a.isDirectory ? -1 : 1
   }
-  return a.name.localeCompare(b.name)
+  return compareFileNames(a.name, b.name)
 }
 
 export function shouldIncludeMobileFileExplorerEntry(entry: MobileDirEntry): boolean {