chore: bump __version__ fallback to 0.12.0 (#44)

Sync the source-tree fallback in __init__.py with pyproject.toml.

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: unamedkr

bindings/python/quantcpp/__init__.py

@@ -15,7 +15,7 @@
     from importlib.metadata import version as _pkg_version
     __version__ = _pkg_version("quantcpp")
 except Exception:
-    __version__ = "0.11.0"  # fallback for editable / source-tree imports
+    __version__ = "0.12.0"  # fallback for editable / source-tree imports
 
 import os
 import sys