Can you recycle runes just to float power/energy without paying for something, specifically to preserve resources when a unit with Deathknell is about to die?

Ruling: You can recycle runes to float power/energy, but you must either have Priority or be in the middle of paying a cost for a card. You cannot float resources at arbitrary times without one of these conditions.

Sequence:

• Wait for a trigger (like Tasty's Deathknell) to go on the chain
• In response to that trigger, use a Reaction to recycle runes and float the resources
• The floated resources remain in your pool (it doesn't empty during or after combat)
• After the trigger resolves, you can use those floated resources

Nuances:

• Your resource pool empties at the end of every turn and after you perform your turn-draw, but NOT during or after combat
• Make sure to communicate clearly with your opponent when floating resources