style: sort Python imports with isort

Add isort configuration (profile=black, line_length=100) to pyproject.toml,
add isort pre-commit hook, and auto-sort imports across all Python source files.

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

python/commands/library_schematic.py

@@ -1,8 +1,9 @@
-from skip import Schematic
+import glob
 
 # Symbol class might not be directly importable in the current version
 import os
-import glob
+
+from skip import Schematic
 
 
 class LibraryManager: