chore: set up pre-commit framework with general hooks

Add .pre-commit-config.yaml with pre-commit-hooks v5.0.0 (trailing
whitespace, end-of-file fixer, yaml/json checks, large file guard,
merge conflict detection). Add minimal pyproject.toml. Auto-fix
trailing whitespace and missing end-of-file newlines across the
codebase.

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

python/commands/library.py

@@ -522,7 +522,7 @@ class LibraryCommands:
                     if path == library_path:
                         library_nickname = nick
                         break
-                    
+
             # Minimal info — always returned even if the parser fails
             info: Dict = {
                 "library": library_nickname,