simple happy-path solution to page history restoration

[janebitovi]

... but only works if there were no variant timelines in the page history before saving.

[do not merge yet]

Will also work as the final solution if any variants get purged from visited page history once a new path is created (which is an option discussed in the past and might be worth consideration again per convo with Mike)

A more complex solution that allows variants is being explored before we make a decision here so the trade-offs will be clear. (creating this PR now because some of this work is relevant to both directions)

[janebitovi]

• [ ] Note: we may want to hide/remove this page history var from the debug panel since it could get quite long

[janebitovi]

code from this was used but closing it because we've landed on a better solution