docs(#100): preserve v0.4 mockups

docs/product/v0.4.0/README.md

@@ -0,0 +1,32 @@
+# v0.4.0 — Current Weekend & Product Truth
+
+Product research references for the v0.4.0 feature sprint.
+
+## Direction
+
+The sprint replaces route-first navigation with a state-aware Weekend experience:
+
+- Weekend is the adaptive home for what happened, what is live, and what is next.
+- Preview content folds into Weekend before a session.
+- Live remains a stable deep link and becomes Weekend's active-session state.
+- Race Hub remains explicit completed-session analysis rather than a primary landing destination.
+- Championship and Briefing remain dedicated destinations.
+- Explore owns secondary discovery; Admin moves to operator utility.
+
+## Mockups
+
+- `mockups/weekend-between-races.png` — desktop between-races/post-weekend state.
+- `mockups/weekend-live.png` — desktop active-session state; the circuit is static sector context, not live GPS.
+- `mockups/weekend-between-sessions-mobile.png` — 390×844 between-session state.
+
+These are directional references, not pixel-perfect specifications. Implementations must preserve the established box-box visual language, accessibility, data constraints, and responsive behavior while satisfying their issue acceptance criteria.
+
+## Constraints
+
+- No OpenF1 REST dependency during active sessions.
+- Public live GPS is not assumed to be available.
+- Championship round numbers exclude tests and cancelled meetings.
+- Connection health, live-session state, archive availability, and local-analysis readiness are separate concepts.
+- Future sessions must not render empty post-session analysis.
+
+The authoritative product decisions and research packet are recorded in GitHub issue #71 under epic #70.