selection decoration bugs

[disconcision]

1. selecting leftwards, indication deco appears offset:

2. below, i started holding shift at the p, and then moved rightwards until i wrapped. note that the selection backing isn't following me; if i go one more char to the right it catches up though:

[dm0n3y]

besides the remaining second issue of partially drawn selection silhouettes, there remain some cases of indentation bugs when selecting across nested bidelimited containers. a minimal example: