Variable page content

Explore how we can make page content variable, so that parts of the text are adapted depending on the state.
Example: if a user had a choice between a spear and a sword earlier, the text passage might say "You grab your sword" or "You grab your spear".
For that we don't want to create two separate pages.

The issue does not identify files, tests, or entry points to inspect. Start by locating how pages and passage text are represented and how prior choices are stored, then determine a design for substituting state-dependent content without duplicating pages. Done means passages can render different text for choices such as sword versus spear.

Written by the indexing model from the issue text.