Implemented Lightweight Observation for Long Input

Implemented lightweight observation for efficiently analyzing long and mixed inputs without performing detailed analysis across the entire input from the start.

The process collects structural and textual signals while preserving their positions in the original input, producing information that later stages can use to decide where evidence analysis and deeper inspection are needed. Consistent results for the same input are also maintained as part of the design.

This established the first implementation stage for connecting the staged long-input analysis architecture to the Scanner processing flow.