docs: add research domains and resource registry

- add local external resources registry
- add research domain contract and per-repository research domains
- add raw fact snapshot governance and validation scripts

Validation:
- make test
- git diff --check HEAD~1..HEAD

Note:
- welcome workflow failed because its action input names are stale; core content CI passed.

docs/research/daotin-ai-coding/raw/github-languages.raw.json

@@ -0,0 +1 @@
+{}