refactor(docsync): move the sync direction type into the docsync model

The pure model imported its direction type from the flow view. The type
now lives in the model, which takes it as the direction parameter, and
the flow view re-exports it for its existing importers.

client/src/components/Files/docsync/DocSyncFlow.tsx

@@ -3,9 +3,9 @@ import { useTranslation } from '../../../i18n/TranslationContext'
 import { DOCUMENT_PROVIDER_ICONS } from '../../shared/DocumentProviderIcons'
 import TrekIcon from '../../shared/TrekIcon'
 import { Badge } from './DocSyncBits'
-import { toggledDirection } from './docSyncModel'
+import { toggledDirection, type SyncDirection } from './docSyncModel'
 
-export type SyncDirection = 'both' | 'pull' | 'push'
+export type { SyncDirection }
 
 export interface FlowHoldings {
   /** Documents this trip has in TREK. */

client/src/components/Files/docsync/docSyncModel.ts

@@ -1,11 +1,12 @@
-import type { SyncDirection } from './DocSyncFlow';
+/** Which way a binding syncs: into the trip, out to the provider, or both. */
+export type SyncDirection = 'both' | 'pull' | 'push';
 
 /**
  * The direction after switching one lane of a binding on or off, or null when that would
  * switch off the last one. The desktop flow bar and the phone's two lane buttons both
  * ask this.
  */
-export function toggledDirection(direction: string, lane: 'push' | 'pull'): SyncDirection | null {
+export function toggledDirection(direction: SyncDirection, lane: 'push' | 'pull'): SyncDirection | null {
   const pushOn = direction === 'both' || direction === 'push';
   const pullOn = direction === 'both' || direction === 'pull';
   const nextPush = lane === 'push' ? !pushOn : pushOn;