Add portable C implementation of 2024/10 topographic map solver

[Copilot]

Portable C version of the Ruby solution for Advent of Code 2024 Day 10 (topographic map pathfinding).

Implementation

• run.c - C99 implementation with custom PositionSet for deduplication, BFS for part 1 (reachable peaks), recursive DFS for part 2 (distinct trails)
• Makefile - Standard build with -std=c99 -O2 for portability and performance
• README.md - Build/run instructions for both implementations
• Sample inputs for verification

Example Usage

# Build and run
make
./run sample_input

# Part 1: 1
# Part 2: 16

The C version accepts input file as optional argument (defaults to 10/input for consistency with Ruby version when run from 2024/ directory).

Original prompt

Do a portable C version of 10/run.rb

Created from VS Code via the GitHub Pull Request extension.

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