john-champagne/srtm-reader ? reverse-engineered prompt

Build me a lightweight library for reading SRTM1 and SRTM3 elevation data in both C and C#.

I want to be able to point it at an SRTM tile file and get elevation values back easily, with a simple API that feels practical for a small app or tool. Keep it minimal and focused, but make sure it handles the common cases for reading the terrain data correctly and reliably.

Please set up the C version and the C# version so they each have a clean way to load a file, read values from it, and work with the elevation grid without a lot of extra setup. If anything about the file format or current best practice is unclear, look up the latest docs online and make sensible choices.

Keep the code lightweight, easy to understand, and ready to use as a small reusable library.