Clarify "snapped" waypoint

Waypoints can be freeform or snapped to an intersection.

When manually creating a neighborhood boundary, they are snapped by default.

When you've picked an autogenerated boundary, the created waypoints are unsnapped. (Which makes sense - theres no guarantee that the severance vertices of the autogenerated boundary fall on intersections).

There's already some copy explaining this, but apparently it's pretty easy to miss. I also didn't really understand what was meant by "snapped" until I became more familiar with the feature.

This doesn't strike me as super urgent, especially if we address #201

The issue is about improving the UI copy explaining 'snapped' vs 'unsnapped' waypoints when creating neighborhood boundaries. Look at the existing UI text in the boundary creation interface, likely in a frontend component or localization file. Compare the behavior for manual vs autogenerated boundaries. The goal is to make the distinction clearer to users without changing functionality.

Written by the indexing model from the issue text.