What are outcome-changing circumstances mentioned in Augury and Divination?

This is one of those naval-gazing questions that may have actual mechanical bearing. Both Augury and Divination predict the outcome of future events:
In the case of Augury

“the results of a specific course of action that you plan to take within the next 30 minutes”

and in the case of Divination

“a specific goal, event, or activity to occur within 7 days”

Where I’m having trouble is deciphering the caveat found in both spells:

The spell doesn’t take into account any possible circumstances that might change the outcome, such as the casting of additional spells or the loss or gain of a companion.

A plain reading of this seems absurd to me, basically amounting to
“outcome X will happen unless circumstances are such that outcome X does not happen”
“outcome X will happen unless it doesn’t.”

For example, a prediction of “you will defeat the evil warlock” might have a possible outcome-altering circumstance of “his archdevil patron makes a surprise appearance and obliterates your entire party in an instant.”

I can see a more charitable reading: “Outcome X will happen unless the party introduces outcome-altering circumstances. And this helps particularly in the case of Augury: There is only so much a party can do to alter the course of the events up to 30 minutes from now. But with Divination’s seven days? How is a party ever to know what contingent facts must hold in order for the predicted outcome to occur? What are “additional spells” when, for some members of the party, spellcasting is done as a matter of course?

How should Augury work when the course of action relies on a skill check?

My party’s Cleric has just picked up Augury. It’s clearly a spell that garners some understandable confusion, but I don’t think this precise question’s been asked before.

How should I, as DM, answer Augury when the good or bad outcomes of a proposed course of action hinge on a skill check, which is random?

To provide a concrete example, suppose the party need to recover some battle plans from within an enemy encampment. In the dead of night, the Cleric casts Augury, proposing: “The rogue sneaks past the sentries and takes it from the command tent”. It’s a fine plan, one I expected them to try, and it will work perfectly if the Rogue rolls at least an 11 on their stealth check – a 50% chance. But if they roll under, the alarm will be raised, and the Rogue will likely be captured.

This isn’t “Nothing”, and it isn’t “Weal-and-Woe” – the result is definitely one of Good or Bad, and it isn’t both. It also isn’t contingent on any subsequent effects that would change the outcome. So how should I answer?

When using the Augury spell, how good or bad does the outcome of the course of action have to be to justify a response of Weal / Woe?

My players are planning to use Augury to decide whether to enter a dungeon, and I’m trying to decide what the outcome of the spell should be.

I can see that some extremes should be obvious: for example, if the dungeon contains four ancient dragons that will annihilate them, it’s Woe. If the dungeon contains a pile of platinum and no dangers at all, it’s Weal. But what if it’s a ‘typical’ dungeon with monsters and traps but also treasure? Does that count as Weal, Woe, Weal and Woe, or neither? What if, again as is often the case, there is danger first before there’s treasure? What if there’s a tough puzzle that might cause them to quit after taking damage but before finding treasure?

If it makes a difference, which I think it might, I would like them to explore this dungeon, and I think they have the skills to survive it and find the treasure. I’ve seen people suggest that Augury is really a way for the PCs to communicate with the DM, and if that’s the case, I would be tempted to say Weal, as code for ‘yes, please do it’. But I don’t want them to feel betrayed when they get (non-lethally) hurt.

As pointed out in comments, Augury only covers events in the next 30 minutes. I’d be interested in answers for both of the following situations:

1) This is a very short dungeon which can be cleared in less than thirty minutes; or

2) The players ask only about whether they should enter the first room of the dungeon – I think this exacerbates the problem because it’s even less clear whether this will be good or bad.

Amulet of Proof against Detection and Augury

One of my player got his hand on an “Amulet of Proof against Detection and Location”, which hides him from divination magic. The description says “While wearing this Amulet, you are hidden from Divination magic. You can’t be targeted by such magic or perceived through magical Scrying sensors.”

Does Augury work on him ? I would think that it would work on the party, but if the question is about an action he (and only him) is going to do ? Does the god answer “well I’m not sure” to the priest ? Or is he not considered as the target of the spell ?