refactor: move research domain to repository root (#58)

Move the complete research domain from docs/research to root-level research, update indexes and path-aware tooling, and align raw snapshot governance and CODEOWNERS.\n\nVerified with make test and GitHub CI.

scripts/check-local-links.py

@@ -109,11 +109,10 @@ def should_skip(path: Path) -> bool:
 def is_research_repository_snapshot(rel: Path) -> bool:
     parts = rel.parts
     return (
-        len(parts) >= 5
-        and parts[0] == "docs"
-        and parts[1] == "research"
-        and parts[3] == "raw"
-        and parts[4] == "repository"
+        len(parts) >= 4
+        and parts[0] == "research"
+        and parts[2] == "raw"
+        and parts[3] == "repository"
     )