Scope captures to specific window

Right now this project works on the entire screen, however it would be beneficial to limit it to a specific window, this would potentially allow smaller screenshots for easier processing, but additionally less worry about leaking random things or introducing unwanted data or noise into our screenshots.

The issue names no files, tests, or capture entry point; start by locating the current whole-screen capture path. Define how a specific window is selected, then verify screenshots contain only that window and exclude unrelated data or noise.

Written by the indexing model from the issue text.