backfill: add impl_tags to all 1,476 metadata files

Added impl_tags section with 5 dimensions:
- dependencies: 14 unique (selenium, scipy, sklearn most common)
- techniques: 24 unique (html-export, annotations, layer-composition)
- patterns: 10 unique (data-generation in 93% of files)
- dataprep: 9 unique (kde, normalization, regression)
- styling: 6 unique (alpha-blending, grid-styling, minimal-chrome)

Cleaned up styling tags:
- Removed 'publication-ready' (too vague, not meaningful)
- Fixed 'custom-colormap' to only tag actual cmap= usage
- Added 'minimal-chrome' where axis('off') is used

Updated tagging rules in prompts/impl-tags-generator.md

Issue #2434

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

Author: MarkusNeusinger

docs/backfill-impl-tags-checklist.md

@@ -132,10 +132,12 @@ Statistical or mathematical transformations.
 
 #### 5. styling - "Which visual style?"
 
-Visual/aesthetic approach.
+Distinctive visual/aesthetic choices that deviate from defaults.
 
 **Typical Values:**
-`publication-ready`, `minimal-chrome`, `custom-colormap`, `alpha-blending`, `edge-highlighting`, `gradient-fill`, `grid-styling`, `dark-theme`
+`minimal-chrome`, `custom-colormap`, `alpha-blending`, `edge-highlighting`, `gradient-fill`, `grid-styling`, `dark-theme`
+
+**Note:** `custom-colormap` is only for continuous color scales (cmap=), not manual color definitions.
 
 ### Impl Tag Example
 

docs/reference/tagging-system.md

@@ -11,6 +11,20 @@ preview_url: https://storage.googleapis.com/pyplots-images/plots/alluvial-basic/
 preview_thumb: https://storage.googleapis.com/pyplots-images/plots/alluvial-basic/altair/plot_thumb.png
 preview_html: https://storage.googleapis.com/pyplots-images/plots/alluvial-basic/altair/plot.html
 quality_score: 95
+impl_tags:
+  dependencies: []
+  techniques:
+  - layer-composition
+  - bezier-curves
+  - hover-tooltips
+  - html-export
+  - custom-legend
+  patterns:
+  - data-generation
+  - iteration-over-groups
+  dataprep: []
+  styling:
+  - alpha-blending
 review:
   strengths:
   - Excellent implementation of a complex alluvial diagram using Altairs declarative

plots/alluvial-basic/metadata/altair.yaml

@@ -11,6 +11,19 @@ preview_url: https://storage.googleapis.com/pyplots-images/plots/alluvial-basic/
 preview_thumb: https://storage.googleapis.com/pyplots-images/plots/alluvial-basic/bokeh/plot_thumb.png
 preview_html: https://storage.googleapis.com/pyplots-images/plots/alluvial-basic/bokeh/plot.html
 quality_score: 92
+impl_tags:
+  dependencies: []
+  techniques:
+  - bezier-curves
+  - custom-legend
+  - annotations
+  patterns:
+  - data-generation
+  - matrix-construction
+  - iteration-over-groups
+  dataprep: []
+  styling:
+  - alpha-blending
 review:
   strengths:
   - Excellent implementation of alluvial diagram from scratch using Bokeh low-level
@@ -25,16 +38,31 @@ review:
   - Legend is positioned far right creating slight visual imbalance
   - Node labels only shown for first and last time points; middle time points could
     benefit from value annotations
-  image_description: |-
-    The plot displays a basic alluvial diagram showing voter migration between four political parties (Democratic, Republican, Independent, Other) across four election years (2012, 2016, 2020, 2024). The visualization uses:
-    - **Colors**: Blue (#306998) for Democratic, Red (#D62728) for Republican, Yellow (#FFD43B) for Independent, Gray (#7F7F7F) for Other
+  image_description: 'The plot displays a basic alluvial diagram showing voter migration
+    between four political parties (Democratic, Republican, Independent, Other) across
+    four election years (2012, 2016, 2020, 2024). The visualization uses:
+
+    - **Colors**: Blue (#306998) for Democratic, Red (#D62728) for Republican, Yellow
+    (#FFD43B) for Independent, Gray (#7F7F7F) for Other
+
     - **Title**: "alluvial-basic · bokeh · pyplots.ai" centered at top
-    - **Subtitle**: "Voter Migration Between Parties (values in millions)" in gray below the title
-    - **Layout**: Four vertical time columns with rectangular nodes representing party sizes, connected by smooth Bezier curve bands showing flow transitions
-    - **Labels**: Left side shows starting values (Democratic 42M, Republican 37M, Independent 15M, Other 6M), right side shows ending values (Democratic 48M, Republican 40M, Independent 13M, Other 2M)
+
+    - **Subtitle**: "Voter Migration Between Parties (values in millions)" in gray
+    below the title
+
+    - **Layout**: Four vertical time columns with rectangular nodes representing party
+    sizes, connected by smooth Bezier curve bands showing flow transitions
+
+    - **Labels**: Left side shows starting values (Democratic 42M, Republican 37M,
+    Independent 15M, Other 6M), right side shows ending values (Democratic 48M, Republican
+    40M, Independent 13M, Other 2M)
+
     - **Time labels**: Bold year labels (2012, 2016, 2020, 2024) at the bottom
+
     - **Legend**: Located on the right side showing all four party colors
-    - **Flow bands**: Semi-transparent (alpha 0.5) with color matching the source category, clearly showing transitions between parties
+
+    - **Flow bands**: Semi-transparent (alpha 0.5) with color matching the source
+    category, clearly showing transitions between parties'
   criteria_checklist:
     visual_quality:
       score: 37

plots/alluvial-basic/metadata/bokeh.yaml

@@ -11,6 +11,19 @@ preview_url: https://storage.googleapis.com/pyplots-images/plots/alluvial-basic/
 preview_thumb: https://storage.googleapis.com/pyplots-images/plots/alluvial-basic/highcharts/plot_thumb.png
 preview_html: https://storage.googleapis.com/pyplots-images/plots/alluvial-basic/highcharts/plot.html
 quality_score: 91
+impl_tags:
+  dependencies:
+  - selenium
+  - pillow
+  techniques:
+  - html-export
+  - annotations
+  - hover-tooltips
+  - custom-legend
+  patterns:
+  - data-generation
+  dataprep: []
+  styling: []
 review:
   strengths:
   - Excellent implementation of alluvial structure using Highcharts sankey with explicit

plots/alluvial-basic/metadata/highcharts.yaml

@@ -11,6 +11,18 @@ preview_url: https://storage.googleapis.com/pyplots-images/plots/alluvial-basic/
 preview_thumb: https://storage.googleapis.com/pyplots-images/plots/alluvial-basic/letsplot/plot_thumb.png
 preview_html: https://storage.googleapis.com/pyplots-images/plots/alluvial-basic/letsplot/plot.html
 quality_score: 91
+impl_tags:
+  dependencies: []
+  techniques:
+  - layer-composition
+  - bezier-curves
+  - html-export
+  - annotations
+  patterns:
+  - iteration-over-groups
+  dataprep: []
+  styling:
+  - alpha-blending
 review:
   strengths:
   - Excellent choice of realistic voter migration data that perfectly demonstrates

plots/alluvial-basic/metadata/letsplot.yaml

@@ -11,6 +11,20 @@ preview_url: https://storage.googleapis.com/pyplots-images/plots/alluvial-basic/
 preview_thumb: https://storage.googleapis.com/pyplots-images/plots/alluvial-basic/matplotlib/plot_thumb.png
 preview_html: null
 quality_score: 91
+impl_tags:
+  dependencies: []
+  techniques:
+  - bezier-curves
+  - patches
+  - manual-ticks
+  patterns:
+  - data-generation
+  - matrix-construction
+  - iteration-over-groups
+  dataprep: []
+  styling:
+  - alpha-blending
+  - minimal-chrome
 review:
   strengths:
   - Excellent implementation of alluvial diagram from scratch using matplotlib low-level

plots/alluvial-basic/metadata/matplotlib.yaml

@@ -11,6 +11,17 @@ preview_url: https://storage.googleapis.com/pyplots-images/plots/alluvial-basic/
 preview_thumb: https://storage.googleapis.com/pyplots-images/plots/alluvial-basic/plotly/plot_thumb.png
 preview_html: https://storage.googleapis.com/pyplots-images/plots/alluvial-basic/plotly/plot.html
 quality_score: 92
+impl_tags:
+  dependencies: []
+  techniques:
+  - hover-tooltips
+  - html-export
+  - annotations
+  - custom-legend
+  patterns:
+  - data-generation
+  dataprep: []
+  styling: []
 review:
   strengths:
   - Excellent alluvial/Sankey diagram implementation using Plotly go.Sankey

plots/alluvial-basic/metadata/plotly.yaml

@@ -11,6 +11,19 @@ preview_url: https://storage.googleapis.com/pyplots-images/plots/alluvial-basic/
 preview_thumb: https://storage.googleapis.com/pyplots-images/plots/alluvial-basic/plotnine/plot_thumb.png
 preview_html: null
 quality_score: 91
+impl_tags:
+  dependencies: []
+  techniques:
+  - layer-composition
+  - bezier-curves
+  - annotations
+  patterns:
+  - wide-to-long
+  - groupby-aggregation
+  - iteration-over-groups
+  dataprep: []
+  styling:
+  - alpha-blending
 review:
   strengths:
   - Excellent implementation of alluvial diagram using plotnine grammar of graphics

plots/alluvial-basic/metadata/plotnine.yaml

@@ -11,6 +11,20 @@ preview_url: https://storage.googleapis.com/pyplots-images/plots/alluvial-basic/
 preview_thumb: https://storage.googleapis.com/pyplots-images/plots/alluvial-basic/pygal/plot_thumb.png
 preview_html: https://storage.googleapis.com/pyplots-images/plots/alluvial-basic/pygal/plot.html
 quality_score: 91
+impl_tags:
+  dependencies:
+  - cairosvg
+  techniques:
+  - bezier-curves
+  - html-export
+  - annotations
+  patterns:
+  - data-generation
+  - matrix-construction
+  - iteration-over-groups
+  dataprep: []
+  styling:
+  - alpha-blending
 review:
   strengths:
   - Excellent visual representation of voter migration with clear flow patterns