android: share a note, and read or edit one shared with you

The editor's menu has Share…, which opens a sheet of who the note is shared
with and lets you add someone at view or edit, change it, or stop sharing;
unlinked, it says sharing needs a server. A note shared to view opens
read-only; at edit only its text can change. Cards say who shared a note
("From Robin") or that yours is shared, and a view-only note's boxes don't
tick.

Also: two core store tests used unwrap_err on a Result<Note>, which needs
Note: Debug; they use err().expect() now.

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

core/src/local/store.rs

@@ -1314,7 +1314,9 @@ mod tests {
     fn a_view_share_changes_nothing_here() {
         let conn = db();
         shared(&conn, "n", "view");
-        let refused = update_note(&conn, "n", &json!({ "body": "mine now" })).unwrap_err();
+        let refused = update_note(&conn, "n", &json!({ "body": "mine now" }))
+            .err()
+            .expect("refused");
         // The words the person sees, exactly: the refusal prints as its message.
         assert_eq!(refused.to_string(), VIEW_ONLY);
         assert!(add_item(&conn, "n", "eggs").is_err());
@@ -1338,7 +1340,9 @@ mod tests {
         assert!(dirty(&conn, "n"));
         add_item(&conn, "n", "eggs").expect("an item is text");
 
-        let pinned = update_note(&conn, "n", &json!({ "pinned": true })).unwrap_err();
+        let pinned = update_note(&conn, "n", &json!({ "pinned": true }))
+            .err()
+            .expect("refused");
         assert_eq!(pinned.to_string(), OWNER_ONLY);
         assert!(update_note(&conn, "n", &json!({ "body": "x", "archived": true })).is_err());
         assert!(trash(&conn, "n").is_err());