Drop placeholder-sized window-memory entries at load

An earlier cleanup deleted five of them from window-memory.json by hand and
they came back within minutes. The reason is that a running compositor holds
the whole table in memory and save_all writes all of it back on the next
window close, so a hand-edited file cannot survive a running session.
Filtering on load is the only point where the fix sticks.

remove_window already refuses to record a size the client never chose, so
nothing new is captured this way; this clears what was written before that
landed. Those entries are self-perpetuating - a remembered size makes the
next launch non-provisional, which forces the client to that size rather
than asking it to pick, which writes the same value back on close - so an
affected app can never escape on its own.

A window genuinely sized exactly 800x632 loses its remembered size once and
gets it back at the next real resize or close. Two tests cover the exact
match and that sharing only one dimension is not enough.

531 tests pass, clippy clean.

0 files changed, 0 insertions, 0 deletions