capture() read any non-None pid/window_id as a request for exact-window
targeting. Several providers emit every declared schema property on every
tool call, zero-filling unused optional integers, so those calls arrive as
pid=0, window_id=0. The exact-target branch was then entered, the caller's
app= was discarded, _positive_int(0) returned None for both ids, and the
capture failed with a message pointing at pid/window_id. For that class of
model capture(app=...) and frontmost capture never worked at all.
Normalize non-positive ids to None before the branch decision so dispatch
falls through to app/frontmost discovery. Malformed non-numeric ids are
deliberately not treated as placeholders: they still reach the existing
validation error instead of being silently ignored.
Fixes#81333
0xGr1mm