FancyZones: give windows with no zone history somewhere to land

Right now FancyZones only places a window automatically if it has been snapped before. With "Move newly created windows to their last known zone" on, an app that was previously zoned goes back to its last zone. But the first time you ever open an app, or any app you have never manually snapped, FancyZones does nothing: the window just opens wherever Windows decides to put it, and you drag it into a zone yourself. There is currently no setting anywhere that changes this. For anyone who reinstalls an app, resets their zone history, or just runs a lot of one-off tools and dialogs, this means FancyZones effectively guides only the windows you have already trained it on, and leaves everything else on its own.

I looked through the existing backlog for anything that already covers this and found two issues that are close but not quite the same thing:

• #9527 is about which layout gets applied to a monitor or virtual desktop that FancyZones has never seen before. It solves "what grid of zones shows up here" for an unrecognized screen. It says nothing about where an individual window, snapped or not, lands inside whatever layout is already active. A monitor could have a perfectly good layout applied and this proposal would still do nothing, because the gap is per-window, not per-monitor.
• #16964 is about pinning a specific application's remembered zone so it stops drifting between its last few positions. That is a fix for existing history, for apps that already have some. It does not help the very common case of a window with no history at all, which is what this issue is about, and it does not extend to windows generally, only to whichever apps you have explicitly locked.

Both are useful and neither one gives a new window, or one from an app you have never zoned, a default place to go. I think this is worth handling on its own rather than folded into either.

What I would propose, roughly: a per-layout setting, off by default and out of the way (collapsed) so it does not clutter the FancyZones settings page for people who do not want it, that lets you pick either a single zone or a contiguous range of zones as the fallback for that layout. When a window has no last-known-zone to go back to (either because the toggle for that is off, or because this is genuinely the first time), and this fallback is configured and still makes sense for the zone count on that monitor, the window goes there instead of nowhere. If last-known-zone history exists and that toggle is on, history would still win, this is only for the gap that's left over once history has nothing to offer.

I'm not attached to the details here and would rather get the direction right before writing any of it. Two things I'd actually like your input on: does this fit where you want FancyZones settings to go, or do you see this differently? And would you rather this live per layout as I described, or as a single global fallback that applies everywhere regardless of which layout is active? I can see arguments either way and would rather build the one you'd actually want to maintain.