chore(plotnine): add metadata for line-retention-cohort

Author: github-actions[bot]

plots/line-retention-cohort/metadata/plotnine.yaml

@@ -0,0 +1,19 @@
+# Per-library metadata for plotnine implementation of line-retention-cohort
+# Auto-generated by impl-generate.yml
+
+library: plotnine
+specification_id: line-retention-cohort
+created: '2026-03-16T20:44:50Z'
+updated: '2026-03-16T20:44:50Z'
+generated_by: claude-opus-4-5-20251101
+workflow_run: 23164943107
+issue: 4572
+python_version: 3.14.3
+library_version: 0.15.3
+preview_url: https://storage.googleapis.com/pyplots-images/plots/line-retention-cohort/plotnine/plot.png
+preview_thumb: https://storage.googleapis.com/pyplots-images/plots/line-retention-cohort/plotnine/plot_thumb.png
+preview_html: null
+quality_score: null
+review:
+  strengths: []
+  weaknesses: []