Debugger hides object members when a pause snapshot is large

When a paused program has a large object graph, the Variables tree can show “additional values not shown” under Self, App, or another object, with no way to expand the missing members. This can hide the very values needed to diagnose a bug. Keep breakpoint pauses responsive while allowing every inspectable object member to be requested from the paused program on demand. Expanding one variable must not make unrelated variables disappear.