A commit that fixes all of the little things I forgot about, but that
are necessary for rendering to function properly.
- (attr. lines) reverse lines before extending above
- (attr. lines) clamp the AttributedLine offset so that there is always
a line with offset 0
- (tree renderer) use meta spaces for the cursor too
- (tree renderer) use correct indent text for cursor
- (tree renderer) fix mypy error by safely ignoring it
- (supply) sort by root id instead of value
- (supply) return id, not list of ids
