Storing piloting status

Nobody has claimed this yet.

*Pain Point*: The distinctions between confirmatory and exploratory work and between pilot and "real" data collection are critical for planning studies and interpreting results, but researchers face challenges in learning new practices as scientific norms change rapidly to reflect our better understanding of their impact.

*Acceptance Criteria*: The standard workflow in designing and starting a study on Lookit includes clear delineation of whether the work is exploratory or confirmatory, and when "real" data collection begins. Researchers can link to preregistration in their study details. Researchers state whether data collection is in "pilot" mode and that information is included in session data.

*Implementation notes/Suggestions*:
* We could modify the display of studies to participants to show whether a study is in the pilot phase and whether it's exploratory - this also provides a foundation for requiring this information in the future, and supporting other states like "demo of a past study". In the future we aim to provide useful templates for Lookit preregistrations as well.
* Could treat from UI perspective as a "state change" (analogous to making active/pausing) rather than something on study edit page (like discoverable/not). Could be an actual additional state (piloting vs active vs paused) or a separate orthogonal state (piloting vs real data collection). For considering actual additional state see https://lookit.readthedocs.io/en/develop/implementation-django-notes.html#why-transitions

Start by reading the linked implementation Django notes on state transitions, then map how study details, participant-facing study displays, and session data currently represent study status. Done means the standard workflow captures exploratory or confirmatory status, pilot or real data collection, and preregistration links, with pilot information included in session data.

Written by the indexing model from the issue text.