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/shouzhengai-cs146s-cn/raw/github-languages.raw.json

@@ -0,0 +1,7 @@
+{
+  "Python": 85300,
+  "JavaScript": 9865,
+  "HTML": 7490,
+  "CSS": 2272,
+  "Makefile": 1404
+}