🎉 Initial commit: project scaffold, agent modes, and gnarly_csv example

- Add .roomodes with four custom Roo agents:
    • excalidraw-to-python  – diagram → typed Python skeleton
    • python-coder          – skeleton → production implementation (design patterns)
    • tester                – pytest suite writer & runner
    • orchestrator          – coordinates the full excalidraw→code→test→execute pipeline
- Add src/csv_grok.py and tests/test_csv_grok.py (CSV diff utility)
- Add examples/gnarly_csv/ with gnarly_csv_delta.py and sample data (rev_a/rev_b)
- Add drawings/ with design.excalidraw and gnarly_csv_files.excalidraw
- Add docs/excalidraw-to-python-agent.md
- Add requirements.txt and .gitignore

docs/excalidraw-to-python-agent.md

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+# 🎨 Excalidraw → Python Agent
+
+## What is this mode?
+
+The **Excalidraw → Python** mode (`excalidraw-to-python`) is a custom Roo agent that reads
+`.excalidraw` diagram files and translates them into **strongly-typed skeletal Python code**.
+
+It never writes implementation logic — it produces well-structured scaffolding with type
+annotations, docstrings, and `# TODO:` markers so a developer can fill in the real logic.
+
+---
+
+## How to activate it
+
+1. Open the Roo chat panel in VS Code.
+2. Click the mode selector (bottom-left of the chat input).
+3. Choose **🎨 Excalidraw → Python**.
+
+Or, if you are already in another mode, ask Roo:
+
+> "Switch to Excalidraw → Python mode and parse `drawings/design.excalidraw`."
+
+---
+
+## What the agent does — step by step
+
+| Step | What the agent looks for | What it produces |
+|------|--------------------------|-----------------|
+| 1 | `rectangle` / `ellipse` / `diamond` shapes + their text labels | Python functions or classes |
+| 2 | `arrow` elements with `startBinding` / `endBinding` | Call-chain / data-flow order |
+| 3 | Free-floating `text` elements (CLI usage, notes) | `argparse` entry-point |
+| 4 | Frame labels | Module / file boundaries |
+
+---
+
+## Rules the agent follows
+
+- Uses **Python 3.10+** type-hint syntax (`X | Y`, `list[str]`, etc.).
+- Imports `from __future__ import annotations` at the top.
+- Every function has a **typed signature** and a **docstring**.
+- Bodies contain only `pass` and `# TODO:` comments.
+- A `if __name__ == "__main__":` block wires up the CLI.
+- Uses `argparse` (stdlib) unless the diagram explicitly mentions another CLI library.
+
+---
+
+## Example
+
+Given the diagram in `drawings/design.excalidraw` the agent produces `src/csv_grok.py`
+(see that file for the full output).
+
+The diagram encodes:
+
+```
+CSV File 1 ──┐
+             ▼
+         Combine (union)  ──►  Analyse (cross-correlate?)
+             ▲
+CSV File 2 ──┘
+
+CLI: csvGrok file1.csv file2.csv -o analysis.txt
+```
+
+---
+
+## Configuration location
+
+The mode is defined in **`.roomodes`** at the project root.  
+That file is the single source of truth for all custom Roo agents in this project.
+
+```jsonc
+// .roomodes
+{
+  "customModes": [
+    {
+      "slug": "excalidraw-to-python",
+      "name": "🎨 Excalidraw → Python",
+      ...
+    }
+  ]
+}
+```
+
+To add more agents, append additional objects to the `customModes` array.