docs: add RSI survey and mechanism-level research papers

docs: add RSI survey and mechanism-level research papers Adds four primary-source research entries to existing README sections, filling the survey and mechanism-level research gaps without changing the taxonomy. All four requested descriptions are preserved verbatim; only README.md changes (four added lines). | Resource | Placement | Target, persistence, ## Codex Review Summary This comment shows the latest Codex review activity on this pull request. | Review | Status | Commit | Review trigger | | --- | --- | --- | --- | | 📝 **Code Review** | ✅ **Completed** <relative-time datetime="2026-10-12T08:17:47.2...