[CLAUDE] Phase2: Form Engine MVP + docs (gotchas, skill, handoff)

Backend Forms:
- Domain/Forms: ContractTemplate (FormCode, Name, ContractType, FileName, StoragePath, Format, FieldSpec JSON, IsActive) + ContractClause
- EF config voi unique FormCode + query filter IsDeleted
- DbSets + IApplicationDbContext update
- Migration AddForms (bang 14 total)
- Packages: DocumentFormat.OpenXml 3.x + ClosedXML 0.105+
- Application/Forms:
  - IFormRenderer interface + RenderResult record
  - FormFeatures.cs: List/Get/Render CQRS
  - IWebHostEnvironmentLocator (abstract IWebHostEnvironment)
- Infrastructure/Forms:
  - DocxRenderer: OpenXml-based placeholder {{field}} replace, handle split runs (gom text tat ca <w:t> trong paragraph, replace, gan lai text dau + clear rest)
  - XlsxRenderer: ClosedXML cell value replace
  - FormRenderer router theo format docx/xlsx
- Api:
  - FormsController: GET /templates (filter type, onlyActive), GET /templates/{id}, POST /templates/{id}/render (return file)
  - WebHostEnvironmentLocator impl
- DbInitializer SeedContractTemplatesAsync: seed 8 template metadata, IsActive=true chi khi file ton tai

Templates vat ly:
- Copy 5 .docx/.xlsx tu FORM/ sang wwwroot/templates/
- 3 .doc (FO-002.02/03/06) chua convert: IsActive=false (Word COM bi stuck luc test, can retry voi DisplayAlerts=0 hoac LibreOffice)
- scripts/convert-doc-to-docx.ps1 (Word COM automation)

Frontend fe-admin:
- types/forms.ts: ContractTemplate + ContractTypeLabel
- pages/forms/FormsPage.tsx: list templates + Render dialog (paste JSON data → download .docx/.xlsx)
- Route /forms them vao App.tsx

Bug fix:
- SpaceProcessingModeValues namespace: wrap EnumValue<> full path
- SaveAs2($path, 16) thay vi SaveAs([ref], [ref]) — PowerShell type issue
- Word COM stuck: kill process, skip .doc cho MVP

Docs (theo yeu cau user):
- docs/gotchas.md MOI: 17 pitfalls nhom theo tech stack / EF Core / OpenXml / JSON / dev workflow
- .claude/skills/form-engine/SKILL.md: placeholder → full spec (algorithm + code pointers + API + limitations)
- .claude/skills/permission-matrix/SKILL.md: placeholder → full spec (BE policy + FE guard + seed + pitfalls)
- docs/HANDOFF.md MOI: brief 5 phut cho session sau (run quickstart + where we are + next steps + file tree + gotchas ref)
- docs/STATUS.md: update cumulative stats + next up Phase 3
- docs/changelog/migration-todos.md: tick Phase 2 iteration 1 items + add iteration 2 list
- docs/changelog/sessions/2026-04-21-1200-phase2-form-engine.md: session log
- CLAUDE.md root: them reference den gotchas + HANDOFF

E2E verified:
- GET /api/forms/templates (onlyActive=false) → 8 templates
- POST /api/forms/templates/{FO-002.05}/render voi data dict → HTTP 200 + file .docx 482KB (Microsoft Word 2007+ OK)

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

CLAUDE.md

@@ -70,6 +70,8 @@ Kiến trúc: **.NET 10 Clean Architecture + 2 React FE (admin + user) + SQL Ser
 | [`docs/forms-spec.md`](docs/forms-spec.md) | Catalog 8 form + quy định mã HĐ |
 | [`docs/database/database-guide.md`](docs/database/database-guide.md) | DB conventions + schema hiện tại + planned + ERD |
 | [`docs/flows/README.md`](docs/flows/README.md) | Index 6 flow (auth, permission, contract create/approve, form render, SLA) |
+| [`docs/gotchas.md`](docs/gotchas.md) | ⭐ 17 bẫy đã gặp — đọc trước khi debug tương tự |
+| [`docs/HANDOFF.md`](docs/HANDOFF.md) | Brief 5 phút: session trước làm gì + P1 tasks tiếp |
 
 ## ⚠️ Kết thúc session