Reveal hidden tree branches on command palette action

[davestewart]

I added some code to scroll into view the current story nav item, but this fails if the nav item is in a collapsed branch.

Not sure of the best way to solve it, but likely moving responsibility for scrolling to NavRoot so it can determine where in the tree the item is, and expand all parent branches if so.

Going forward, a store / composable might be a better way set up all data rather than doing it in the page and passing along to child components.

[timhanlon]

It was originally a composable but there was issues with Vite circular imports, see #17