Make perpetual mana cost overlay reflect all cost modifiers

[MostCromulent]

As noted in #10258 current "perpetual mana cost" overlay only accounts for perpetual effects (+commander tax if that PR is merged) but not battlefield state cost modifiers.

Ideally the overlay would be adapted to so it accurately tells users: how much will it cost to cast this card? accounting for all relevant cost effects (since this is ultimately what user wants to know).

However this raises more complex architectural issues including:

• overlap with current logic for conclusively determining mana cost when spell is cast and put on the stack,
• performance considerations for calculating mana costs for all castable cards for purpose of the overlay, rather than just a single card when actually cast by user.

AI spec document and potential implementation plan here.

Would need input from devs before considering taking this any further, particularly re: AI's proposed architecture and whether performance mitigations are sufficient to make this at all workable.

[tool4ever]

Mostly not in favor of complicating the code for a visual helper which will lack accuracy in a way completely non-obvious to most users :/

checkStaticAbilities() is the natural invalidation point (runs after zone transitions, ability changes, counter changes). It fires 5-10+ times per turn.

that's quite the understatement 🤡

a turn in only a:

• 2-player game
• basic only decks
• where nothing happens besides passing priority

1. already requires 36 calls
2. playing a land will add 14 calls
3. having only Henzie on the field vs. AI alone quickly leads to 100s of more calls

for any non trivial boardstate the performance would be terrible 💣