ark: Cap console input that is "too large" for R's buffer

[DavisVaughan]

Extracted from #1326 (comment)

Resolving that is mostly a frontend thing, but we should still tweak the ark behavior to cap console input that is too large, simply throwing away anything beyond the buffer capacity, rather than the current behavior which ends up putting you in an invalid state. This is similar to what RStudio does IIUC (but RStudio also chops up the input as we are planning on doing)

[juliasilge]

In Positron 2024.01.0 (Universal) build 141, I can put very large input into the R console and R is still happy and fine afterward:

buffer.mov