Battle Skills and Kingdom Renown Gain Clearer Progression

What changed

• Battle Skills now use a long-run staged breakthrough curve: Levels 1–25 remain approachable, Levels 25–75 slow substantially, and Levels 75–100 form the true mastery climb.
• Boss final blows remain valuable extra breakthrough opportunities, but no longer bypass large parts of normal Battle Skill progression.
• The active Battle Skill and every Skill tooltip now show the exact current breakthrough chance and progression phase.
• Treasury Expertise now keeps fractional precision at every rank. Even Rank 1 visibly affects hourly interest instead of disappearing through rounding.
• Local Treasury explains the complete calculation with base interest, the Treasury Expertise multiplier, Empire Corruption, Rune Corruption and the exact next-hour Gold gain.
• The base Treasury capacity is now 2,000,000,000 Gold. Royal Vaults still raises every owned Kingdom by 1,000,000,000 per rank, and Gold already above a new capacity is preserved until withdrawn.
• Guard Command now strengthens real Guard battles, and Fortification Engineering strengthens Walls, Moats, Bastions and Siege Batteries without incorrectly multiplying an unfortified Army.
• Existing Battle Skill levels, Kingdom Renown, upgrades, Treasury Gold and accumulated fractional interest are all preserved.