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/openai-codex/domain.yml

@@ -0,0 +1,32 @@
+version: 1
+repo:
+  name: openai/codex
+  source_name: openai/codex
+  url: https://github.com/openai/codex
+research:
+  domain_id: openai-codex
+  domain_name: openai/codex 研究域
+  primary_direction: coding-agent-tooling
+  role: 官方 coding agent 工具源码
+  priority: 1
+  why_study: 适合作为 AI coding agent 工具实现、权限、沙箱和 CLI 交互研究对象。
+github_observed:
+  observed_at: '2026-07-03'
+  source: gh repo view
+  stars: 95112
+  forks: 14105
+  archived: false
+  language: Rust
+  license: apache-2.0
+  default_branch: main
+  pushed_at: '2026-07-02T22:05:48Z'
+  updated_at: '2026-07-02T21:01:16Z'
+  latest_release: rust-v0.142.5
+  homepage: ''
+  topics: []
+source_evidence:
+  file: ChatGPT-中文Vibe Coding仓库 (2).md
+  line: 56
+maintenance:
+  fact_policy: GitHub 动态字段只代表 observed_at 当日快照，更新结论前必须重新核验。
+  split_policy: 本目录已经是一等研究域；更深分析放入本目录新增文档。