add build development phases

dev/shared-working-context/frontend/requests/for-backend.md

@@ -0,0 +1,15 @@
+# Frontend → Backend requests (append-only)
+
+The frontend lane appends here when it needs a contract that doesn't exist yet, finds a shape mismatch,
+or needs a new field/filter/endpoint. The backend agent reads this at the start of each phase and
+delivers fixes in its own change. **Frontend never edits backend code to "fix" a gap — it requests it.**
+
+<!-- TEMPLATE — copy per request
+## REQ-NNN — <short title> — filed by frontend-phase-N-bM — <YYYY-MM-DD>
+- **Need:** <endpoint / field / filter / shape>
+- **Why:** <which screen/flow needs it>
+- **Proposed shape:** <JSON sketch, optional>
+- **Status:** open | delivered in backend-phase-K
+-->
+
+_(no requests yet)_