Promote OSS cleanup, tests, CI, and docs from dev to main

[ppon1086]

This PR promotes the recent OSS cleanup and packaging improvements from dev to main.

Included in this merge

• improved core validation and reporting flow
• added adapter and harness utilities
• rewrote README for adoption, integration, and quickstart
• updated minimal fixture logs for current CLI format
• added smoke tests for validate and report
• added GitHub Actions CI
• added CONTRIBUTING and CHANGELOG

Why

This moves the repository to a cleaner public baseline that is easier to:

• install
• test
• understand
• reuse
• integrate into other RAG tooling workflows

It also makes the repo more suitable for public adoption, listing, and future releases.

Notes

This PR is intended to make main the new stable public branch after the recent cleanup and OSS-oriented improvements on dev.