Windows sessions on the self-hosted lane settled one or two of seven sends on
the controlled prompt and charged the silence tier for the rest (issue 2487).
The marker is written by the shell's own prompt function and the printable tail
by the same render, so a tail that arrives past `idleSilenceMs +
handoffGraceMs` means a stalled delivery, not an absent prompt.
`dsh-terminal-bash` gains a validated `promptTailGraceMs` bound (default 0,
which reproduces the previous bound exactly). While a send has seen the marker
and its printable tail has not arrived, the silence bound grows by it. The
pwsh Loader-composition case sets 5000 ms, the host class the bound is for, and
still fails when no marker appears at all.
Tianyi Cui
3693c2b402