In a scaletest determining the effect of a greedy agent/user we discovered that a single web terminal (reconnecting PTY) can use up all of coderd CPU resources.

The following pprof dumps are from the middle of the "Phase 5: Web Terminal Traffic" as highlighted in the graph:

pprof-allocs-coder-64c4996857-cdckw-1701443704.gz
pprof-block-coder-64c4996857-cdckw-1701443704.gz
pprof-goroutine-coder-64c4996857-cdckw-1701443704.gz
pprof-heap-coder-64c4996857-cdckw-1701443704.gz
pprof-mutex-coder-64c4996857-cdckw-1701443704.gz
pprof-profile_seconds_10-coder-64c4996857-cdckw-1701443704.gz
pprof-trace_seconds_5-coder-64c4996857-cdckw-1701443704.gz

It's fairly easy for a user to do this by accident, as demonstrated in #11036.

Refs #8556 #11036