docs(ios): open the referenced row from a foreign key preview

ios/index.mdx

@@ -107,15 +107,22 @@ On iPhone Duo the system draws the toolbar and the tab bar down the side of the
 
 ### Browsing
 
-A row in the list previews four of its fields, and eight where the display is wide enough. Search the table list by name. A PostgreSQL materialized view sits under **Views** and opens read only. Page a table at 50, 100, 200, or 500 rows, jump to a page number, sort by a column, search text columns, and stack filters with AND or OR. A foreign key value previews the row it points at.
+A row in the list previews four of its fields, and eight where the display is wide enough. Search the table list by name. A PostgreSQL materialized view sits under **Views** and opens read only. Page a table at 50, 100, 200, or 500 rows, jump to a page number, sort by a column, search text columns, and stack filters with AND or OR.
+
+To follow a foreign key, tap the link under its value on a row, or long-press a row in the list and pick the key. A sheet previews the row it points at, titled with the table and, when it differs from the one open, the schema. A value in the preview that is itself a foreign key opens the next row in the same sheet, and **Back** returns one step. **Open Table** opens that table filtered to the key, and when one row matches it lands on that row, ready to edit. **Back** then returns to the filtered list and to the row you started from. While that row has an edit open, **Open Table** is dimmed.
+
+<Frame caption="One more tap from the preview to the row in its table">
+  <img className="block dark:hidden" src="/images/ios-foreign-key-preview.png" alt="Customer preview sheet with a SupportRepId link to Employee and an Open Table button, beside the Customer row screen showing 1 of 1" />
+  <img className="hidden dark:block" src="/images/ios-foreign-key-preview-dark.png" alt="Customer preview sheet with a SupportRepId link to Employee and an Open Table button, beside the Customer row screen showing 1 of 1" />
+</Frame>
 
 **Table Structure** lists columns, indexes, and foreign keys, read only. An index shows its key columns and expressions in key order, then any `INCLUDE` columns and a partial index's `WHERE` clause. On Redshift the index list holds the DISTKEY and SORTKEY columns.
 
 On Redis the list holds the current database's keys. A key opens by type: a string's value, a hash's fields, a list's elements by index, a set's members, a sorted set's members and scores, a stream's entries. There is no search, sort, filter or **Table Structure** for a key.
 
 ### Editing
 
-Tap a row to open it full screen, page between rows, edit values, toggle one to `NULL`, and save. An emptied date, number or boolean field saves `NULL`, and in a NOT NULL column it keeps its value; an emptied text field saves an empty string. While you edit, **Cancel** takes the place of the back button and asks before it throws away a changed value, and so does **Connections** in another tab. Inserting and deleting rows, and truncating or dropping a table, are here too; a PostgreSQL foreign table offers neither Truncate nor Drop. Editing needs a primary key.
+Tap a row to open it full screen, page between rows, edit values, toggle one to `NULL`, and save. An emptied date, number or boolean field saves `NULL`, and in a NOT NULL column it keeps its value; an emptied text field saves an empty string. While you edit, **Cancel** takes the place of the back button and asks before it throws away a changed value, and so does **Connections** in another tab. Inserting and deleting rows, and truncating or dropping a table, are here too; a PostgreSQL foreign table offers neither Truncate nor Drop. Editing needs a primary key, and a row whose key holds binary data opens read only.
 
 A new row starts with every column on **DEFAULT**, which leaves that column out of the `INSERT` so the database fills it in. The badge beside a field switches it between **DEFAULT**, **NULL** and a typed value, and **NULL** is offered on nullable columns only. Generated columns are never written, and an auto-increment key stays on **DEFAULT** until you type one.