feat: 2025 day 4 - #8

+ atest
+ getNbs
+ input
+ neighs
+ part1
+ part2
+ test

## summary with just the declaration names:
./scripts/declarations_diff.sh

## more verbose report:
./scripts/declarations_diff.sh -l

The doc-module for script/declarations_diff.sh contains some details about this script.

Current commit 2d6c6485a1
Reference commit 9b188cc9fc

You can run this locally as

./scripts/technical-debt-metrics.sh pr_summary

• The relative value is the weighted sum of the differences with weight given by the inverse of the current value of the statistic.
• The absolute value is the relative value divided by the total sum of the inverses of the current values (i.e. the weighted average of the differences).