chore: bump version to 0.1.2

[rlippmann]

Summary

• bump the package version from 0.1.1 to 0.1.2
• prepare a patch release containing the recent preprocessor validation contract correction and compound directive detection improvements

Notes

• validate_preprocessor_output(...) and parse_preprocessor_output(...) now validate preprocessor output only and no longer accept source_input
• heuristic preprocessing now conservatively abstains when multiple canonical directive starts are detected
• this release allows downstream consumers, including example integrations, to update to the corrected drafter behavior