web, core, desktop: share a note with a group, and Settings → Groups

The Share dialog lists people and groups in one picker and shows a group share
as its name and member count. Settings gains a Groups section for the admin:
create, rename, delete, and add or remove people.

The core client reads the directory's groups and group shares (ShareTarget:
a member or a group); the desktop command takes user_id or group_id.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

frontend/src/adapters/local.ts

@@ -16,7 +16,7 @@ import type { Device } from "../stores/devices";
 import type { TitleEntry } from "../stores/titles";
 import type { User } from "../stores/session";
 import type { PublicConfig } from "../stores/config";
-import type { DeviceToken, ImportResult, Member, NoteShare, Repo } from "./repo";
+import type { DeviceToken, Directory, ImportResult, NoteShare, Repo } from "./repo";
 
 const NEEDS_SERVER = "That's not available offline — connect a server to use it.";
 
@@ -95,9 +95,15 @@ export const local: Repo = {
   // Sharing is between accounts on a server, so these go to the linked one (#5175).
   // Unlinked, each rejects with the core's explanation, which the dialog shows.
   shares: {
-    directory: () => invoke<Member[]>("shares_directory"),
+    directory: () => invoke<Directory>("shares_directory"),
     list: (noteId) => invoke<NoteShare[]>("shares_list", { noteId }),
-    share: (noteId, userId, permission) => invoke<NoteShare[]>("shares_share", { noteId, userId, permission }),
+    share: (noteId, target, permission) =>
+      invoke<NoteShare[]>("shares_share", {
+        noteId,
+        userId: "user_id" in target ? target.user_id : null,
+        groupId: "group_id" in target ? target.group_id : null,
+        permission,
+      }),
     unshare: (noteId, shareId) => invoke<NoteShare[]>("shares_unshare", { noteId, shareId }),
   },
 };