Suggestion for custom study

I would like to propose adding two distinct features to Custom Study:
1. A new 'Cram all reviewed cards' option that allows users to review all previously studied cards in a temporary session, without rescheduling them or affecting the FSRS algorithm
2. A new 'Preview a set number of days ahead' option that allows users to review cards scheduled for a specific number of days in the future, again, without rescheduling them or impacting the FSRS algorithm.

Start by locating the Custom Study entry point and tracing how temporary review sessions currently select cards and interact with scheduling. Define separate flows for all reviewed cards and cards scheduled a chosen number of days ahead. Done means both options review the intended cards without rescheduling them or affecting FSRS.

Written by the indexing model from the issue text.