Add initial implementation of Python helpers and CLI tools

- Create .gitignore to exclude build artifacts
- Add README.md with project description and installation instructions
- Implement pyproject.toml for package metadata and script entry points
- Add console output helpers for command-line scripts
- Implement environment file loading functionality
- Add JSON file I/O helpers
- Create token decoder CLI for decoding JWT claims
- Implement serve-markdown CLI for serving Markdown files as HTML

python_helpers/files.py

@@ -0,0 +1,37 @@
+"""JSON file I/O helpers for command-line scripts."""
+
+import json
+from pathlib import Path
+
+from python_helpers.console import fail
+
+
+def load_json(path, missing_hint=None):
+    """Load and parse a JSON file, failing with a consistent message if it is missing.
+
+    Args:
+        path: path to the JSON file.
+        missing_hint: optional extra line of guidance to print if the file is missing.
+
+    Returns:
+        The parsed JSON content.
+    """
+    if not Path(path).exists():
+        message = f"{path} not found!"
+        if missing_hint:
+            message += f"\n{missing_hint}"
+        fail(message)
+    with open(path, "r") as f:
+        return json.load(f)
+
+
+def save_json(path, data, indent=2):
+    """Save data to a file as JSON.
+
+    Args:
+        path: path to write to.
+        data: JSON-serializable data to write.
+        indent: indentation level to format the JSON with.
+    """
+    with open(path, "w") as f:
+        json.dump(data, f, indent=indent)