fix(desktop): make project "Add folder" picker remote-gateway aware

The new-project / add-folder dialog (PR #49037) picked folders via the
native Electron dialog (pickDefaultProjectDir), which only browses the
LOCAL machine. On a remote gateway that picks a path that doesn't exist
on the backend where sessions actually run.

Route pickProjectFolder() through selectDesktopPaths({directories,
multiple:false}) — the same remote-aware path the retired right-sidebar
picker used: local mode opens the native directory dialog, remote mode
browses the backend filesystem via the in-app RemoteFolderPicker. Seed
it with the backend's default cwd on remote so it opens somewhere useful.

apps/desktop/src/store/projects.test.ts

@@ -1,4 +1,4 @@
-import { beforeEach, describe, expect, it } from 'vitest'
+import { beforeEach, describe, expect, it, vi } from 'vitest'
 
 import {
   $projectScope,
@@ -6,9 +6,21 @@ import {
   ALL_PROJECTS,
   enterProject,
   exitProjectScope,
+  pickProjectFolder,
   refreshWorktrees
 } from './projects'
 
+vi.mock('@/lib/desktop-fs', () => ({
+  desktopDefaultCwd: vi.fn(),
+  isDesktopFsRemoteMode: vi.fn(),
+  selectDesktopPaths: vi.fn()
+}))
+
+const fs = await import('@/lib/desktop-fs')
+const desktopDefaultCwd = vi.mocked(fs.desktopDefaultCwd)
+const isDesktopFsRemoteMode = vi.mocked(fs.isDesktopFsRemoteMode)
+const selectDesktopPaths = vi.mocked(fs.selectDesktopPaths)
+
 describe('project scope', () => {
   beforeEach(() => {
     window.localStorage.clear()
@@ -50,3 +62,38 @@ describe('worktree refresh', () => {
     expect($worktreeRefreshToken.get()).toBe(before + 1)
   })
 })
+
+describe('pickProjectFolder', () => {
+  beforeEach(() => {
+    vi.clearAllMocks()
+  })
+
+  it('uses the remote-aware directory picker locally (no backend default cwd probe)', async () => {
+    isDesktopFsRemoteMode.mockReturnValue(false)
+    selectDesktopPaths.mockResolvedValue(['/local/repo'])
+
+    await expect(pickProjectFolder()).resolves.toBe('/local/repo')
+    expect(selectDesktopPaths).toHaveBeenCalledWith({ defaultPath: undefined, directories: true, multiple: false })
+    expect(desktopDefaultCwd).not.toHaveBeenCalled()
+  })
+
+  it('seeds the picker with the backend cwd on a remote gateway', async () => {
+    isDesktopFsRemoteMode.mockReturnValue(true)
+    desktopDefaultCwd.mockResolvedValue({ branch: 'main', cwd: '/backend/work' })
+    selectDesktopPaths.mockResolvedValue(['/backend/work/repo'])
+
+    await expect(pickProjectFolder()).resolves.toBe('/backend/work/repo')
+    expect(selectDesktopPaths).toHaveBeenCalledWith({
+      defaultPath: '/backend/work',
+      directories: true,
+      multiple: false
+    })
+  })
+
+  it('returns null when the picker is cancelled (empty selection)', async () => {
+    isDesktopFsRemoteMode.mockReturnValue(false)
+    selectDesktopPaths.mockResolvedValue([])
+
+    await expect(pickProjectFolder()).resolves.toBeNull()
+  })
+})

apps/desktop/src/store/projects.ts

@@ -2,6 +2,7 @@ import { atom } from 'nanostores'
 
 import { liveSessionProjectId, type SidebarProjectTree } from '@/app/chat/sidebar/projects/workspace-groups'
 import type { HermesGitBranch } from '@/global'
+import { desktopDefaultCwd, isDesktopFsRemoteMode, selectDesktopPaths } from '@/lib/desktop-fs'
 import { persistentAtom } from '@/lib/persisted'
 import { activeGateway, ensureActiveGatewayOpen } from '@/store/gateway'
 import { setSidebarAgentsGrouped } from '@/store/layout'
@@ -732,19 +733,18 @@ export async function copyPath(path: null | string): Promise<void> {
   }
 }
 
-// Open the native directory picker (reuses the Electron default-project-dir
-// chooser). Returns the chosen absolute path, or null when cancelled.
+// Pick a folder for a project. Routes through the remote-aware folder picker
+// (selectDesktopPaths): a remote gateway browses the BACKEND filesystem via the
+// in-app RemoteFolderPicker — where sessions actually run — while local mode
+// uses the native directory dialog. Returns the chosen absolute path, or null
+// when cancelled. Seeded with the backend's default cwd on remote so the picker
+// opens somewhere useful instead of "/".
 export async function pickProjectFolder(): Promise<null | string> {
-  const pick = window.hermesDesktop?.settings?.pickDefaultProjectDir
-
-  if (!pick) {
-    return null
-  }
-
   try {
-    const result = await pick()
+    const defaultPath = isDesktopFsRemoteMode() ? (await desktopDefaultCwd())?.cwd : undefined
+    const [dir] = await selectDesktopPaths({ defaultPath, directories: true, multiple: false })
 
-    return result.canceled ? null : result.dir
+    return dir || null
   } catch {
     return null
   }