[CLAUDE] Docs: chốt rule timing unit test (1 bảng 5-row compact)

- rules.md §7: thêm section "Khi nào viết test — timing rule"
  4 case (feature mới/bug fix/critical algorithm/spec change) + 1 skip list
- CLAUDE.md root: 1 dòng quick reference timing rule
- User confirm pattern Phase 1-8 (test-after pragmatic) là default cho solo dev
- Test-before BẮT BUỘC chỉ khi: bug fix (regression test) + critical algorithm
- Spec change KHÔNG ngừng test — update test cũ + code, commit chung

Commit MD-only → CI skip (path filter gotcha #41), 0s deploy.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

CLAUDE.md

@@ -89,7 +89,7 @@ tests/
 dotnet test SolutionErp.slnx     # chạy cả 2 test project
 ```
 
-**Quy tắc:** mỗi feature mới có guard logic / business rule → thêm test trước khi commit. Bug found in production → 1 regression test added before merge. Detail xem `docs/architecture.md §11` + `docs/rules.md §7`.
+**Quy tắc timing test:** feature mới = test-after (UAT ổn → viết). Bug fix = test-before BẮT BUỘC (reproduce → fix). Critical algorithm (codegen/guard/financial/security) = test-before merge. Spec change = update test cũ + code chung commit. Skip: DTO mapping, CRUD master, FE snapshot. Detail `docs/rules.md §7`.
 
 ### CI/CD pipeline (3 fix lớn 29/04)