style: apply Black formatting to all Python files

Add [tool.black] config to pyproject.toml and Black hook to
.pre-commit-config.yaml (rev 26.3.1), then auto-format all Python
source and test files with line-length=100, target-version=py310.

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

python/commands/__init__.py

@@ -10,10 +10,10 @@ from .design_rules import DesignRuleCommands
 from .export import ExportCommands
 
 __all__ = [
-    'ProjectCommands',
-    'BoardCommands',
-    'ComponentCommands',
-    'RoutingCommands',
-    'DesignRuleCommands',
-    'ExportCommands'
+    "ProjectCommands",
+    "BoardCommands",
+    "ComponentCommands",
+    "RoutingCommands",
+    "DesignRuleCommands",
+    "ExportCommands",
 ]