[CLAUDE] Docs: chốt Session 15 wrap-up — tooltip diagnose + drastic refactor DEFER

Session 15 (2026-05-07) docs update:

STATUS.md:
- Last updated Session 15 (1 commit `835cc7f` tooltip + working tree
  drastic refactor revert)
- Recently Done row Session 15 chi tiết (diagnose + plan drastic +
  attempt 12 file edits + REVERT decision)

HANDOFF.md:
- TL;DR Session 15 prepend với 2 phần: Diagnose tooltip + Drastic
  refactor DEFER decision
- 4 cảnh báo Session 16+: Drastic refactor pending (8-10h dedicated
  hoặc fallback Approach Y), Task 2 sample seed pending, schema-diagram
  defer cron audit, Hard blockers giữ nguyên

migration-todos.md:
- Phase 9 + Session 15 block với 1 task done (tooltip) + 1 defer
  (drastic refactor) + memory entry note
- Defer Session 16+ list

Session log NEW `2026-05-07-2600-tooltip-defer-drastic.md`:
- Bối cảnh user UAT báo button silent disabled
- Phần 1 — Diagnose tooltip (root cause + fix UX + "trùng ID" KHÔNG
  phải bug FE)
- Phần 2 — Plan drastic refactor flat workflow → DEFER:
  * User spec mới (Phòng × Cấp × Users[] flat)
  * Plan 6 chunk + estimate scope realistic ~8-10h
  * Attempt 12 file working tree edits → REVERT decision
  * Memory entry capture decision rule
- Plan organization sau S15 (defer queue)

Memory entry NEW `feedback_drastic_refactor_scope.md`:
- Quy tắc: drastic refactor cần dedicated session, scope conservative
  2x buffer
- Anti-patterns mid-session big refactor + commit broken state
- Defer pattern (revert working tree → document → memory entry → surface
  trade-off cho user)
- Cross-ref `feedback_per_chunk_commit.md` discipline

🎉 Session 15 wrap-up. Cumulative since session start (13h17): 16 commit
(1 button removal + 6 PE N-stage + 5 Contract N-stage + 1 3-button +
1 Session 14 wrap-up + 1 tooltip + 1 Session 15 wrap-up).

Verify: dotnet test 96 pass + working tree clean.

Defer Session 16+ priority order:
1. Drastic refactor flat workflow (dedicated session ~8-10h)
   OR fallback Approach Y (FE flat UI 5 phòng, 1-2h)
2. Task 2 sample data seed N-stage
3. Hard blockers Ops (UAT, SMTP, etc.)

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

docs/changelog/migration-todos.md

@@ -157,6 +157,20 @@ Session log: `2026-04-28-chot-session-4-budget.md`.
 
 ## 📝 Phase 9 — UAT + Ops + carry over (Session 6+ active)
 
+### ✅ Session 15 done (2026-05-07) — Tooltip diagnose "Lưu & Gửi Duyệt" + drastic refactor flat workflow DEFER (1 commit)
+
+User UAT live báo button "Lưu & Gửi Duyệt" KHÔNG hoạt động + suy đoán "trùng ID". Diagnose: silent disabled khi `nextPhases` không có forward phase. Add tooltip + dialog warning. "Trùng ID" KHÔNG phải bug FE.
+
+- [x] **Tooltip diagnose** (commit `835cc7f`) — fe-admin + fe-user PeDetailTabs: compute `forwardPhase` once + `submitDisabledReason` reason string + button title attribute hover + dialog confirm show forward phase label explicit. Build pass × 2. KHÔNG đụng BE.
+- [⏸] **Drastic refactor flat workflow** — User chốt "bỏ phase enum hoàn toàn, dùng ChoDuyet=10 đơn nhất + currentStepIndex tracking". Attempt edit working tree 12 file Domain/Configurations/DbContext, realize scope realistic ~8-10h (PolicyRegistry + Service + App CQRS + 12 tests + FE Designer + Migration 21 + Docs) vượt session. REVERT working tree về `835cc7f` clean. **Defer Session 16+** dedicated session.
+
+**Decision memorized:** add memory `feedback_drastic_refactor_scope.md` — drastic refactor cần dedicated session với context fresh, scope estimation conservative (2x buffer), tránh mid-session big refactor (risk session context deep + breaking states giữa chunk).
+
+**Defer Session 16+:**
+- [ ] Drastic refactor flat workflow (Mig 21, ~8-10h, dedicated session) — flat WorkflowStep với DepartmentId+PositionLevel, drop InnerStep, PE/Contract CurrentWorkflowStepIndex tracking, Phase enum simplify ChoDuyet=10, Service rewrite, Designer FE rewrite.
+- [ ] Hoặc fallback Approach Y — FE Designer flat UI giới hạn 5 phòng (auto-assign Phase behind scenes), ROI 1-2h, KHÔNG drastic.
+- [ ] Task 2 sample data seed N-stage (block trên DesignTime vs Runtime DB)
+
 ### ✅ Session 14 done (2026-05-07) — PE 3-button workflow Duyệt/Trả lại/Từ chối (1 commit)
 
 User chỉ thị thay 2-button approval (Duyệt + Reject mơ hồ) bằng 3 hành động rõ: