Saving entity id to link submissions in analysis

Can use natural id or entity id with `/data/meta/entity/@id`

Example:
- https://docs.google.com/spreadsheets/d/1kod6tUKV3CoX8AsdNs7sMWmNF9SBQKFVksAOtbqn6oQ/edit?gid=1068911091#gid=1068911091
- https://docs.google.com/spreadsheets/d/1pft3qi9Vg4FGPQWaMvBR7xcHfj95KJCGxlZs-I0UIAo/edit?gid=1068911091#gid=1068911091

Start by reviewing the two linked Google Sheets examples and the `/data/meta/entity/@id` reference in the ODK documentation. Locate the relevant documentation page, clarify whether natural IDs and entity IDs are supported for linking submissions in analysis, and document the confirmed behavior with an accurate example.

Written by the indexing model from the issue text.