ConPTY DSR CPR on resize can interrupt in-flight (long-term) DCS (or APC or ...)

This will impact tmux control mode, as ConPTY will send `\x1B` to terminal and promptly terminate the in-flight exchange.

All in-band signaling from ConPTY must be suppressed when passing through a DCS. Fortunately, nobody will be querying the cursor position to know it hasn't updated.

Start by tracing ConPTY resize handling, especially the DSR/CPR response path and how in-flight DCS or APC exchanges are tracked. Reproduce a resize during a long-running control-mode exchange and verify that ConPTY emits no in-band signaling while the DCS is active.

Written by the indexing model from the issue text.