This fixes#21 by changing the existing "tail" attachment point (`#ff0000`) to be called the "anchor" attachment point, since that's primarily what we're using it for. It also adds a brand-new "tail" attachment point with color `#be0027`, which is expected to be oriented in the direction the tail should point (not the _opposite_ direction of the tail, which is how the old tail attachment point was oriented).
Note that this change means, for now, that no symbols have tail attachment points. An error will be logged in the console when viewing the "Creature!" page for now because of this (since the default composition attaches a symbol to the tail), but as soon as Nina updates the SVGs, this should go away.
This attempts to manually scale the strokes on creatures so they aren't affected by scale.
The weird thing here is that applying `vector-effect="non-scaling-stroke"` does not appear to do the trick--rather, it makes all the strokes look _super heavy_. So in this PR we scale the stroke by the inverse of whatever we're cumulatively scaling by when we're drawing something.
This fixes a bunch of bugs in our attachment-related code, and in so doing refactors things to make more sense, adds more tests, and also adds documentation.
Here we attempt to use arrowhead symbols in SVGs to allow artists to specify the orientation of attached symbols, rather than attempting to auto-detect it via projecting the circles onto the shape and using the normal as we did in #2.
It seems like this logic is both much simpler and less error-prone, especially around corners. It also gives artists much more control over the placement of attachments.
The one fragile aspect of the implementation is that we assume the first point of the arrow shape is its tip, and that the third point is its indented bottom. This appears to be consistent across all of Nina's SVGs, so far at least...
Atul Varma