Update AGENTS.md with guidance on running scripts in offline environments

- Clarify that `refresh_data.py` should not be run in Codex/CI due to lack of internet access.
- Emphasize the need for local data in `data/fred.db` before executing scripts.
- Adjust descriptions for `startup.sh` and `Makefile` to reflect changes in usage and requirements.

AGENTS.md

@@ -1,19 +1,21 @@
 # AGENTS.md — Guidance for OpenAI Codex
 
 ## Execution Commands
-- **Always** invoke Python scripts via the startup wrapper, which now installs dependencies globally and then runs your code under the system Python:
+- **Always** invoke Python scripts via the startup wrapper, which installs dependencies globally and then runs your code under the system Python:
   
   ```bash
   ./startup.sh --offset <months> --end <YYYY-MM-DD> --extend-years <N>
 ````
 
+* **Never** call `refresh_data.py` from within a Task Command. This environment has **no internet access**, so attempts to fetch external data will fail. Data in `data/fred.db` must already be present.
+
 ## Project Overview
 
 This repository, **python\_charts**, provides a framework for fetching economic time series from FRED, storing them locally, and producing custom matplotlib charts with configurable parameters. The core components are:
 
-* **`startup.sh`**: Single‐entrypoint script to install dependencies globally, fetch data, and run specified commands under system Python.
+* **`startup.sh`**: Single‐entrypoint script to install dependencies globally, ensure local data is present, and run specified commands under system Python.
 * **`Makefile`**: Convenient high‐level targets (`install`, `data`, `plot`, `plot‐custom`, `test`, `clean`) that funnel through `startup.sh` for reproducible builds.
-* **`scripts/refresh_data.py`**: Downloads UNRATE and DCOILWTICO series into `data/fred.db`.
+* **`scripts/refresh_data.py`**: Downloads UNRATE and DCOILWTICO series into `data/fred.db`—**only run in an internet-connected environment**, not in Codex/CI.
 * **`scripts/lagged_oil_unrate_chart_styled.py`**: Generates the lagged oil vs. unemployment chart with fixed axes styling and log scale.
 
 Future extensions will add additional custom chart scripts under `scripts/`, all driven by the same bootstrapping and command conventions.
@@ -36,11 +38,14 @@ Future extensions will add additional custom chart scripts under `scripts/`, all
   ./startup.sh --offset 12 --end 2025-05-31 --extend-years 5
   ```
 
-* **Data refresh**:
+* **Data refresh (offline environments)**:
 
-  ```bash
+  * **Do not** run `refresh_data.py` in Codex/CI — data must already be in `data/fred.db`.
-  ./startup.sh scripts/refresh_data.py
+  * To update data in an internet-connected shell, run:
-  ```
+
+    ```bash
+    python scripts/refresh_data.py
+    ```
 
 * **Run tests**:
 
@@ -58,7 +63,7 @@ Future extensions will add additional custom chart scripts under `scripts/`, all
 
 * **Python**: Target version ≥ 3.8. Use type hints for all function signatures. Follow PEP8 with Black formatting.
 * **Bash**: `startup.sh` uses `set -euo pipefail`.
-* **Makefile**: Use tab‐indented commands. All targets should funnel through `startup.sh`.
+* **Makefile**: Use tab-indented commands. All targets should funnel through `startup.sh`.
 
 ## Testing & Validation