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/aider-ai-aider/raw/github-languages.raw.json

@@ -0,0 +1,12 @@
+{
+  "Python": 1333453,
+  "CSS": 67532,
+  "Shell": 66537,
+  "Tree-sitter Query": 64845,
+  "JavaScript": 60909,
+  "HTML": 44976,
+  "PowerShell": 19648,
+  "Dockerfile": 4405,
+  "SCSS": 1957,
+  "Ruby": 196
+}