chore(altair): add metadata for bar-basic

Author: github-actions[bot]

plots/bar-basic/metadata/altair.yaml

@@ -0,0 +1,18 @@
+# Per-library metadata for altair implementation of bar-basic
+# Auto-generated by impl-generate.yml
+
+library: altair
+specification_id: bar-basic
+
+preview_url: https://storage.googleapis.com/pyplots-images/plots/bar-basic/altair/plot.png
+preview_html: https://storage.googleapis.com/pyplots-images/plots/bar-basic/altair/plot.html
+
+current:
+  version: 0
+  generated_at: 2025-12-11T22:54:47Z
+  generated_by: claude-opus-4-5-20251101
+  workflow_run: 20150015719
+  issue: 612
+  quality_score: null  # Updated after review
+
+history: []