I'm happy to begin and end with the fiction, but if as a player the game lets me try to establish some of that fiction (that's not yet been established) via action declaration incuding intent, and on a successful roll that fiction becomes established, then why wouldn't I always declare intents that benefit my character and or its goals?
Perhaps you would do that. But that doesn't mean literally any benefit you could phrase in the English language is now open to you!
Why would a player--for example--ever do anything "CvC", as you put it, when doing so is nearly always counterproductive in the long term and at least risking so in the short term? Because it's what would make sense for them.
If your own approach falls prey to the same standard, what does that tell us?
We know the Desert Rose exists because that's been established in the fiction, and we think we know who currently owns/has it.
Sure. That's fine.
What hasn't been established in the fiction is its location.
Correct. Since that has not been established, the player cannot unilaterally will it into existence. It might be the case that the GM frames a scene which reveals its position, generally as the result of a player move of some kind. Or it might be the case that the conversation that is play just naturally results in a slow accumulation of knowledge about where the ruby might be and where it definitely can't be until only one answer makes any sense. That's also a valid path, that doesn't specifically require anyone (GM or player) to declare anything specific. For example, one might overhear a guard saying that their employer doesn't trust the safes anymore, so they hid the ruby elsewhere. That doesn't establish where the ruby
is, but it now conclusively establishes that no safe will contain the ruby, no matter where the PC(s) might look. Later, a bribed magician might say they helped furnish various magical means of storage to the possessor, which positively identifies that some kind of magical means were used to secret the ruby way. Finally, the player might hear the possessor curse at being unable to check on the ruby because their basement panic room is warded against planar travel--which, when combined with the other pieces of information, means that it must have been secreted away using
Leomund's secret chest or something similar.
Both positive evidence ("it was hidden by magic") and negative evidence ("it was not put in a safe") both help zero in on the final answer. Sometimes, a sufficient mass of positive and negative evidence will leave only one valid answer remaining. Sometimes, an explicit confirmation will do the trick instead, e.g. instead of overhearing that vague comment, they might find a magic laboratory...with luxurious treasure chests and identical matching miniature chests, explicitly calling out
Leomund's secret chest as the true answer.
In the total absence of establishing fiction, the player does not get to simply author whatever they like, whenever they like. That's against the rules. What is done must
follow from the fiction, not simply invent fiction from whole cloth that happens to be convenient to the player. (At least in PbtA games. I can't speak to other systems, having not played them, but I'm certain they will have analogous requirements.)
It could be in the safe in the wall in the tycoon's house, it could be in the bank down the street, it could be on his yacht in the harbour, it could be in his pocket, or any of a hundred other possible places.
Yep. And as long as that information remains unknown to you, you
do not have the ability to just fiat declare "It's here!"
And so if we've managed to break into his house and get to his safe, I can declare "I pick open the safe to find the Desert Rose ruby". Task - pick the safe. Intent - find the ruby.
Nope! That's exactly where you've gone wrong, and where I've repeatedly
said you've gone wrong, but you refuse to consider it.
Instead, it is: Task - pick the safe. Intent -
steal what is inside. That's a valid and unequivocally well-established intent, and with the paucity of established fiction, as you've explicitly said (the player
does not have any particularly good reason to think this specific safe has the ruby), it's just about the
only unequivocally well-established intent you can pursue here. But, as always, play is a conversation, so it is possible that the group might agree that other intents are valid, given the situational context (aka "the fiction").
Just as with my other examples: Task - pick the lock. Intent - escape the prison cell I'm in. That's an extremely well-established intent for any situation where you know you're in prison and want to get out! But perhaps you might have other intents, such as "trick the warden into my cell", presumably so you can lock them up like they've locked you up. That might also be warranted, again, if the conversation that is play justifies such an act. (Maybe it's established fiction that this warden is quite cruel and likes to personally torture prisoners--so having the lock picked could let you bum rush the guard.) Or: Task - pick the lock. Intent - begin my heist of this manor-house. As before, an unequivocally well-established intent.
Just because one's intent isn't
utterly impossible doesn't mean it's okay. You need more than that. Depending on the exact thing, you might need a
lot more than that. With the ruby, you'd need to be pretty much certain that that is, in fact, where the ruby is kept, otherwise you're talking about the player simply
willing the world to be whatever it is they'd like it to be at the most convenient time,
which is not how these games work. And I
know you've been told that, repeatedly, just in this thread alone, not even counting the many previous times.
And if the examples I've seen earlier are correct, a full success (roll of 10+ in some systems) will give me both task AND intent, meaning that by my success I've not only just established the location of the Rose but I've also now got my mucky mitts on it. And if I fail, it's not there. I suppose success-with-complication could mean among other things that I open the safe but the ruby's not there.
Only if the intent is a warranted one--which, usually, means that you are building
from established fiction to that intent. As you've--explicitly!--said, the ruby's exact location HAS NOT been established in the fiction. Just fiat declaring that the ruby's location IS IN FACT right here in this specific safe definitely no questions asked isn't kosher,
because there isn't establishing fiction for that. Perhaps you could dig up somewhere a system so badly-constructed, so horrendously awful, that such a thing is in fact okay, but I assure you that no such system I've ever used would permit this. Period. It simply isn't okay to make that kind of leap, and the rules tell you so if you read them. Just as the GM has rules that bind them, the players have rules that bind
them (and generally, rather a lot more of them!)
What this makes impossible, however, is the result of "I fail but the ruby is in fact in the safe"; because the ruby's location has to remain quantum so if I fully succeed (10+) in searching for it on the yacht or somewhere else it can be there waiting for me. Or so I've been told, anyway, though not in those exact terms.
But the ruby's position isn't quantum. It just isn't actually known right now.
Why would you think it was quantum? Who, among those telling you about these games that you (self-professed) do not play and don't know very well, is saying that the ruby's position is quantum?
A "quantum" thing means it could genuinely be anywhere. An unknown thing simply means...we don't know enough to know where it is. We're going to have to
discover where it is first, in order to find it! That's...kind of the point of finding it?
Otherwise, by your logic, every time you don't know where your keys are IRL, they are in fact in each and every possible place they could theoretically be, simply because you don't know where they are yet.