Update AGENTS.md and scripts for global dependency installation

- Revise instructions in AGENTS.md to clarify that Python scripts should be run via `startup.sh`, which now installs dependencies globally.
- Enhance project overview and command sections for better clarity on usage.
- Update coding standards to reflect Python version requirements and Bash script practices.
- Improve formatting and organization of command examples for better readability.

AGENTS.md

@@ -1,17 +1,18 @@
 # AGENTS.md — Guidance for OpenAI Codex
 
 ## Execution Commands
-- **Always** invoke Python scripts via the startup wrapper to activate dependencies:
+- **Always** invoke Python scripts via the startup wrapper, which now installs dependencies globally and then runs your code under the system Python:
   
   ```bash
   ./startup.sh --offset <months> --end <YYYY-MM-DD> --extend-years <N>
+````
 
 ## 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 bootstrap a Python venv, install dependencies, fetch data, and run specified commands under the venv interpreter.
-* **`Makefile`**: Convenient high-level targets (`install`, `data`, `plot`, `plot-custom`, `test`, `clean`) that funnel through `startup.sh` for reproducible builds.
+* **`startup.sh`**: Single‐entrypoint script to install dependencies globally, fetch data, 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/lagged_oil_unrate_chart_styled.py`**: Generates the lagged oil vs. unemployment chart with fixed axes styling and log scale.
 
@@ -21,51 +22,71 @@ Future extensions will add additional custom chart scripts under `scripts/`, all
 
 ### Primary Commands
 
-* **Bootstrap & default plot**: `./startup.sh` or `make plot` — runs the lagged-oil chart with an 18‑month offset.
-* **Custom plot**: `./startup.sh --offset 12 --end 2025-05-31 --extend-years 5` or `make plot-custom ARGS="--offset 12 --end 2025-05-31 --extend-years 5"`.
-* **Data refresh**: `./startup.sh scripts/refresh_data.py` or `make data`.
-* **Run tests**: `./startup.sh pytest -q` or `make test`.
+* **Bootstrap & default plot**:
+
+  ```bash
+  ./startup.sh
+  ```
+
+  Installs/upgrades dependencies globally and runs the default lagged‐oil chart with an 18-month offset.
+
+* **Custom plot**:
+
+  ```bash
+  ./startup.sh --offset 12 --end 2025-05-31 --extend-years 5
+  ```
+
+* **Data refresh**:
+
+  ```bash
+  ./startup.sh scripts/refresh_data.py
+  ```
+
+* **Run tests**:
+
+  ```bash
+  ./startup.sh pytest -q
+  ```
 
 ### Argument Rules
 
-* Arguments beginning with `--` are forwarded to the default chart script.
-* If the first token is a `.py` script or executable, it is invoked under the venv’s Python.
-* Otherwise, commands are executed directly (e.g. linters, test frameworks).
+* If the first token starts with `--`, it’s forwarded to the default chart script.
+* If the first token names a `.py` script, it’s executed via `python <script>`.
+* Otherwise, commands are executed directly (e.g., `pytest`, `flake8`).
 
 ## Coding Standards
 
-* **Python**: Target version 3.12. Use type hints for all function signatures. Follow PEP8 with **Black** formatting.
-* **Bash**: `startup.sh` must use `set -euo pipefail` and always call `$VENV_DIR/bin/python` to avoid system‑Python mismatches.
-* **Makefile**: Use tab‑indented commands. All tasks should funnel to `startup.sh`.
+* **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`.
 
 ## Testing & Validation
 
-* **Automated tests**: No current tests; add pytest modules under `tests/` following the pattern `test_*.py`.
+* **Automated tests**: Add pytest modules under `tests/` following the pattern `test_*.py`.
 * **Data mocking**: For new chart scripts, mock FRED downloads via monkeypatching `pandas_datareader.data.DataReader`.
 
 ## Extending with New Charts
 
-1. **Create a new script** under `scripts/`, for example `scripts/custom_chart.py`.
-2. **Implement** a `main()` accepting `--start`, `--end`, `--offset` or custom args using `argparse`.
-3. **Leverage** `startup.sh` invocation: add usage example in your script’s docstring.
-4. **Update** the `Makefile` if you need a dedicated target, otherwise users can call:
+1. **Create** `scripts/custom_chart.py`.
+2. **Implement** a `main()` with `argparse` for `--start`, `--end`, `--offset`, etc.
+3. **Invoke** via:
 
    ```bash
    ./startup.sh python scripts/custom_chart.py --your-args
    ```
+4. **Optionally** add a Makefile target if desired.
 
 ## CI / Codex Integration
 
-* In Codex cloud or CLI tasks, set the **Setup Script** to `./startup.sh install data` to ensure dependencies and data are ready.
-* **Task Commands** should call `make plot` or `make test`, which delegates to `startup.sh`.
-* **AGENTS.md** is automatically loaded by Codex to understand structure and commands.
+* **Setup Script** →
 
-## PR & Commit Guidelines
+  ```bash
+  chmod +x startup.sh && ./startup.sh
+  ```
+* **Task Command** →
 
-* Prefix branches/PRs with `feature/` or `fix/`.
-* Commit messages: `<type>(<scope>): <description>` (e.g. `feat(charts): add custom inflation plot`).
-* Include screenshots or saved chart outputs under `outputs/` for visual verification.
-
----
+  ```bash
+  ./startup.sh --offset 18
+  ```
 
 *End of AGENTS.md — tailored for python\_charts repo*