chore: bump version to 0.18.0 (#97)

Covers #96: the preview-gated record_deployments flag and the
dependency-chaining fix, needed by mitodl/ol-infrastructure#5600.


Claude-Session: https://claude.ai/code/session_019mvaFgGzBYBL2aatAZ2mJG

Co-authored-by: Claude Sonnet 5 <noreply@anthropic.com>

Author: blarghmatey

pipeline_lib/pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "ol-concourse"
-version = "0.17.0"
+version = "0.18.0"
 description = "Python DSL for programmatically building Concourse CI/CD pipelines"
 authors = [{ name = "MIT Open Learning", email = "odl-devops@mit.edu" }]
 requires-python = ">=3.13"