Update copilot instructions

.github/copilot-instructions.md

@@ -63,6 +63,37 @@ DATA_DIR/
 - `entropice.dashboard`: Streamlit visualization app
 - `entropice.utils`: Paths, codecs, types
 
+## Organisation of the Dashboard
+
+- `entropice.dashboard.app`: Main Streamlit app, entry point, imports the pages
+- `entropice.dashboard.pages`: Individual dashboard pages - functions which handle data loading and building each page, always called `XXX_page()`
+- `entropice.dashboard.sections`: Reusable Streamlit sections - functions which build parts of pages, always called `render_XXX()`
+- `entropice.dashboard.plots`: Plotting functions for the dashboard - functions which create plots, always called `create_XXX()` and return plotly figures
+- `entropice.dashboard.utils`: Dashboard-specific utilities, also contain data loading functions
+
+### Note on deprecated use_container_width parameter of streamlit functions
+
+**❌ INCORRECT** (deprecated):
+```python
+st.plotly_chart(fig, use_container_width=True)
+```
+
+**✅ CORRECT** (current API):
+```python
+st.plotly_chart(fig, width='stretch')
+```
+
+**Common width values**:
+- `width='stretch'` - Use full container width (replaces `use_container_width=True`)
+- `width='content'` - Use content width (replaces `use_container_width=False`)
+
+This applies to:
+- `st.plotly_chart()`
+- `st.altair_chart()`
+- `st.vega_lite_chart()`
+- `st.dataframe()`
+- `st.image()`
+
 ## Testing & Notebooks
 
 - Production code belongs in `src/entropice/`, not notebooks