Add year_2025 folder structure with Day 1 and Day 2 puzzle solutions

[Copilot]

• Create year_2025 folder in src/ with init.py
• Create day_1 subfolder with solution (Secret Entrance)
  • Implemented dial rotation logic with modular arithmetic
  • Part 1: Count times dial lands on 0 after rotation
  • Part 2: Count every click where dial passes through or lands on 0
• Create day_2 subfolder with solution (Gift Shop)
  • Implemented repeated sequence detection
  • Part 1: Sum all invalid product IDs (repeated digit patterns)
  • Part 2: Count all invalid product IDs
• Create matching test structure in tests/year_2025/
• All tests passing
• Fix Flake8 F824 errors (unused global declarations) in:
  • src/year_2021/day-9/day9.py
  • src/year_2022/day_11/code.py

Original prompt

Make a folder for this year and copy in the question for day 1

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[ericlevicky]

@copilot Solve it and do the same for day 2

[Copilot]

@copilot Solve it and do the same for day 2

Implemented solutions for both puzzles in commit abc5774:

Day 1 (Secret Entrance): Dial rotation puzzle - tracks landing/crossing position 0 using modular arithmetic.

Day 2 (Gift Shop): Invalid product ID detection - finds numbers with repeated digit sequences (e.g., 55, 1010, 123123) and sums/counts them.

Both have full test coverage and are passing.

[ericlevicky]

@copilot the tests failed, fix them

[Copilot]

@copilot the tests failed, fix them

Fixed in cbb20e2. The CI was failing due to pre-existing Flake8 F824 errors (unused global declarations) in src/year_2021/day-9/day9.py and src/year_2022/day_11/code.py. Removed the unnecessary global statements - they were only reading/mutating module-level variables, not assigning to them.