docs: start frontend mvp milestone

.planning/REQUIREMENTS.md

@@ -68,6 +68,22 @@ interview-ready after each short practice loop.
 
 ## v2 Requirements
 
+### Frontend MVP
+
+- [ ] **WEB-01**: User can open a web app served by the Go service.
+- [ ] **WEB-02**: User can create a diagnostic interview session from the web
+  app.
+- [ ] **WEB-03**: User can answer a diagnostic question and see rubric feedback.
+- [ ] **WEB-04**: User can see learner memory, readiness, and next challenge
+  after answering.
+- [ ] **WEB-05**: Operator can ingest source material from the web app.
+- [ ] **WEB-06**: Operator can inspect ontology candidate concepts, edges, and
+  gaps.
+- [ ] **WEB-07**: Operator can generate and inspect teaching asset prompt
+  candidates.
+- [ ] **WEB-08**: Web UI includes loading, empty, and error states for the MVP
+  flows.
+
 ### General Student Expansion
 
 - **GEN-01**: Support non-interview learning tracks.
@@ -100,12 +116,16 @@ interview-ready after each short practice loop.
 | PROG-01..PROG-05 | Phase 4 | Complete |
 | ONTO-01..ONTO-04 | Phase 5 | Complete |
 | ASSET-01..ASSET-03 | Phase 6 | Complete |
+| WEB-01..WEB-03 | Phase 7 | Pending |
+| WEB-04 | Phase 8 | Pending |
+| WEB-05..WEB-08 | Phase 9 | Pending |
 
 **Coverage:**
 - v1 requirements: 28 total
-- Mapped to phases: 28
+- v2 frontend requirements: 8 total
+- Mapped to phases: 36
 - Unmapped: 0
 
 ---
 *Requirements defined: 2026-04-26*
-*Last updated: 2026-04-26 after Phase 6 execution.*
+*Last updated: 2026-04-26 after v2 Frontend MVP milestone start.*