docs: note multi-chart VegaLiteAgent output

Document that VegaLiteAgent can produce more than one chart from a single
request, each in its own editable tab alongside an "All" overview.

Author: ghostiee-11

docs/configuration/agents.md

@@ -23,7 +23,7 @@ Lumen includes eight agents automatically. You don't need to configure anything.
 | Agent | What it does |
 |-------|-------------|
 | **SQLAgent** | Writes and runs SQL queries |
-| **VegaLiteAgent** | Creates charts and visualizations |
+| **VegaLiteAgent** | Creates one or more charts from a single request (each in its own editable tab, with an "All" overview) |
 | **DeckGLAgent** | Creates 3D map visualizations for geographic data |
 | **ChatAgent** | Answers questions and provides guidance |
 | **SourceAgent** | Fetches data from configured source controls |

docs/getting_started/using_lumen_ai.md

@@ -18,6 +18,9 @@ Here are some ideas to spark your exploration:
 - "Show me a scatter plot of 'flipper_length_mm' vs 'body_mass_g'."
 - "Create a histogram of 'bill_length_mm'."
 - "Show me a bar chart of average values by species."
+- "Create separate charts of average body mass by species and average flipper length by species."
+
+When a request calls for more than one chart, each chart opens in its own tab that you can edit, alongside an "All" tab that shows every chart together.
 
 **Complex queries:**