app: fix workspace flicker when switching directories

[Brendonovich]

• Navigating between sessions in different directories (workspaces, projects) causes DirectoryLayout to tear down and remount its children as it uses <Show keyed>
• Remounted children load a bunch of new async data via createResource
• This is expected to pause the navigation via a Transition, but instead navigation was happening and the Session route Suspense was showing its fallback
• This occurs due to DirectoryLayout's resolved being set after an async operation outside of the reactive graph (in this case in an effect)
  • Navigation creates transition -> Updates location -> Transition ends (unaware of async in DirectoryLayout) -> Effect runs -> Components remount + route switches -> Async resources fetched outside of transition (causes Suspense flicker)
• The fix is to source resolved from its own createResource, so that Solid knows that fetching resolved should participate in transitions, causing async resources created by children when remounting to also participate in the transition
  • Navigation creates transition -> Updates location -> Resource runs -> Components remount -> Async resources fetched -> Transition ends + Route switches (no flicker!)