Issue #259 reports detached 'pebrel-hook.exe pi <prompt-json>' helpers from
1.9.0 lingering after the host closed and blocking the installer's file
replacement. The forwarding deadline that fixed#258 already bounds every
source; pin the reported Pi path with real-process regressions: five
concurrent prompt notifications against a wedged single-instance receiver
must all exit within the bound, and a prompt notification without a host
must exit silently on every platform.