feat: add config module with load_config function

Add TOML configuration file support with:
- ConfigError exception class for config-related errors
- load_config() function to parse TOML files with proper error handling
- Tests for missing file and invalid TOML syntax scenarios

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

src/zzpyjenkins/config.py

@@ -0,0 +1,22 @@
+"""Configuration file handling."""
+
+from pathlib import Path
+import tomllib
+
+
+class ConfigError(Exception):
+    """Raised when configuration is invalid or missing."""
+
+    pass
+
+
+def load_config(config_path: Path) -> dict:
+    """Load and parse TOML config file."""
+    if not config_path.exists():
+        raise ConfigError(f"Config file not found: {config_path}")
+
+    try:
+        with open(config_path, "rb") as f:
+            return tomllib.load(f)
+    except tomllib.TOMLDecodeError as e:
+        raise ConfigError(f"Invalid TOML syntax: {e}") from e

tests/__init__.py

@@ -0,0 +1 @@
+# Tests package

tests/test_config.py

@@ -0,0 +1,29 @@
+"""Tests for config module."""
+
+import tempfile
+
+import pytest
+from pathlib import Path
+
+from zzpyjenkins.config import load_config, ConfigError
+
+
+def test_load_config_file_not_found():
+    """Test load_config raises error when config file doesn't exist."""
+    with pytest.raises(ConfigError) as exc_info:
+        load_config(Path("/nonexistent/path/config.toml"))
+    assert "Config file not found" in str(exc_info.value)
+
+
+def test_load_config_invalid_toml():
+    """Test load_config raises error for invalid TOML syntax."""
+    with tempfile.NamedTemporaryFile(mode="w", suffix=".toml", delete=False) as f:
+        f.write("invalid toml [[[[")
+        temp_path = Path(f.name)
+
+    try:
+        with pytest.raises(ConfigError) as exc_info:
+            load_config(temp_path)
+        assert "Invalid TOML syntax" in str(exc_info.value)
+    finally:
+        temp_path.unlink()