Add adaptive difficulty scaling based on player performance

[Mkalbani]

Description

Difficulty tiers are currently static per puzzle. Add an adaptive system that nudges difficulty up or down based on the player's recent accuracy and hint usage, so sessions stay appropriately challenging without requiring manual tier selection.

Acceptance Criteria

• DifficultyTracker struct records rolling accuracy and hint-usage over the last N puzzles
• Difficulty adjustment algorithm documented in docs/difficulty.md with the exact thresholds used
• --adaptive CLI flag opts into adaptive mode (off by default to preserve existing behavior)
• Adjustment is bounded so difficulty cannot skip more than one tier per puzzle
• Unit tests simulate streaks of correct/incorrect answers and assert expected tier transitions

[ebubeb683-ship-it]

Hello boss, Please assign this issue to me. i checked it out and im confident i will solve it
my eta is 4 hours

[egwujiohaifesinachiperpetual-max]

Hello boss, Please assign this issue to me. i checked it out and im confident i will solve it
my eta is 4 hours

[Menjay7]

Hi! I came across this issue and would love to work on it. I have experience with similar tasks and I'm confident I can investigate, implement a clean solution, and thoroughly test it before submitting a PR. If the issue is still open, I would appreciate it if you could assign it to me. I’ll prioritize this immediately and ensure a reliable solution is delivered as soon as possible. Thank you!

[jaynomyaro]

Hi! I’m a full-stack developer with a strong blockchain background, and I’m confident I can resolve this issue quickly and effectively. I’ll deliver a clean, reliable solution with immediate attention to detail, ensuring it’s completed as soon as possible. Please assign it to me—I’m ready to get started right away.

[grantfox-oss]

🦊 GrantFox — @Menjay7 has been assigned to this issue as part of the Official Campaign | FWC26 campaign!

Next steps:

1. Open a Pull Request referencing this issue (e.g., Closes #28)
2. Your PR will be reviewed by the ThinknetCollective maintainers

Good luck! Track your progress on GrantFox.