Svelte 5 cleanups

[dabreegster]

These are a long tail of non-blocking problems leftover from migrating to Svelte 5.

• Breaking: drawing a freehand line of filters doesn't show the line consistently. It stops after so many points or moving too fast?
• In edit/NeighbourhoodMode.svelte, don't call renderNeighbourhood() twice at startup
• Reintroduce a Popup wrapper that plumbs props succinctly
• Clean up places with the verbose $props interfaces -- inline the declaration or maybe go Vue-style and do let props: { ... } = $props
• Try to fix prettier formatting again (htmlWhitespaceSensitivity) -- see NeighbourhoodBoundarySummary and Modals for bad problems

[dabreegster]

https://svelte.dev/docs/svelte/context implies you can setContext on something $derived, but it isn't working for us -- layers/NeighbourhoodRoadLayer.svelte isn't seeing updates to gj.maxShortcuts. I'm going to see if we can stop using context and plumb explicitly, which feels a bit safer anyway.

[dabreegster]

OK, Svelte 5 rolled forward with a fix, hopefully good now.

[dabreegster]

Breaking: drawing a freehand line of filters doesn't show the line consistently. It stops after so many points or moving too fast?

I tried this again now in both dev/prod builds and can't reproduce -- it works fine. Mystified, but oh well?