feat: add GenesysCX study and fix Streamlit chart key collisions

- Add 202512_GenesysCX TEI study (config, seed data, notebooks, README)
  with NPV $10.8M / ROI 266% including AI-token cost line
- Add explicit `key` parameter to all chart wrappers in app/components
  to prevent StreamlitDuplicateElementId errors when the same figure
  type renders across Summary/Benefits/Costs tabs
- Render benefits bar and cost pie charts on their respective tabs
- Add benefits_vs_costs_by_year chart wrapper

app/views/costs.py

@@ -4,6 +4,7 @@ from __future__ import annotations
 
 import streamlit as st
 
+from app.components import charts
 from app.components.tables import df_to_values, value_editor
 from app.utils import icon
 
@@ -50,3 +51,18 @@ def render(client: TEIClient, tool: dict) -> None:
             "are end-of-year cashflows. Costs are risk-adjusted upward "
             "(higher risk → higher cost)."
         )
+
+    if values:
+        st.divider()
+        col_pie, col_year = st.columns(2)
+        with col_pie:
+            charts.cost_pie(values, key=f"costs_tab_pie_{public_id}")
+        with col_year:
+            benefit_values = [
+                v
+                for v in safe(client.get_values, public_id) or []
+                if v.get("table") == "benefits"
+            ]
+            charts.benefits_vs_costs_by_year(
+                benefit_values, values, key=f"costs_tab_by_year_{public_id}"
+            )