spec: add bar-stacked-labeled specification (#3507)

## New Specification: `bar-stacked-labeled`

Related to #3504

---

### specification.md

# bar-stacked-labeled: Stacked Bar Chart with Total Labels

## Description

A stacked bar chart that displays multiple data series stacked on top of
each other with total value labels prominently shown above each bar
stack. This variant combines part-to-whole visualization with explicit
numerical annotations, making it easy to read both individual segment
contributions and cumulative totals at a glance. The total labels
eliminate the need for mental arithmetic when comparing overall values
across categories.

## Applications

- Comparing quarterly sales by product line with clear total revenue
figures for executive presentations
- Displaying project budget breakdowns by task category with visible
total costs for each project phase
- Visualizing survey response distributions with total respondent counts
labeled for each question

## Data

- `category` (categorical) - Labels for each bar group on the x-axis
(e.g., quarters, departments, regions)
- `component` (categorical) - The different series being stacked within
each bar (e.g., product lines, cost types)
- `value` (numeric) - Size of each segment representing the measured
quantity
- Size: 3-8 categories with 2-5 stacked components recommended for
readability
- Example: Quarterly revenue by product category, department expenses by
cost type

## Notes

- Total labels should be placed directly above each complete bar stack
with clear formatting
- Use a consistent number format for labels (e.g., rounded integers, one
decimal place, or with units)
- Ensure adequate vertical space above the tallest bar for label
placement
- Consider using a slightly larger or bold font for total labels to
distinguish from segment labels
- Segment labels within the bars are optional but can enhance
readability for larger segments

---

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---
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plots/bar-stacked-labeled/specification.md

@@ -0,0 +1,27 @@
+# bar-stacked-labeled: Stacked Bar Chart with Total Labels
+
+## Description
+
+A stacked bar chart that displays multiple data series stacked on top of each other with total value labels prominently shown above each bar stack. This variant combines part-to-whole visualization with explicit numerical annotations, making it easy to read both individual segment contributions and cumulative totals at a glance. The total labels eliminate the need for mental arithmetic when comparing overall values across categories.
+
+## Applications
+
+- Comparing quarterly sales by product line with clear total revenue figures for executive presentations
+- Displaying project budget breakdowns by task category with visible total costs for each project phase
+- Visualizing survey response distributions with total respondent counts labeled for each question
+
+## Data
+
+- `category` (categorical) - Labels for each bar group on the x-axis (e.g., quarters, departments, regions)
+- `component` (categorical) - The different series being stacked within each bar (e.g., product lines, cost types)
+- `value` (numeric) - Size of each segment representing the measured quantity
+- Size: 3-8 categories with 2-5 stacked components recommended for readability
+- Example: Quarterly revenue by product category, department expenses by cost type
+
+## Notes
+
+- Total labels should be placed directly above each complete bar stack with clear formatting
+- Use a consistent number format for labels (e.g., rounded integers, one decimal place, or with units)
+- Ensure adequate vertical space above the tallest bar for label placement
+- Consider using a slightly larger or bold font for total labels to distinguish from segment labels
+- Segment labels within the bars are optional but can enhance readability for larger segments

plots/bar-stacked-labeled/specification.yaml

@@ -0,0 +1,28 @@
+# Specification-level metadata for bar-stacked-labeled
+# Auto-synced to PostgreSQL on push to main
+
+spec_id: bar-stacked-labeled
+title: Stacked Bar Chart with Total Labels
+
+# Specification tracking
+created: 2026-01-09T15:23:21Z
+updated: null
+issue: 3504
+suggested: MarkusNeusinger
+
+# Classification tags (applies to all library implementations)
+# See docs/reference/tagging-system.md for detailed guidelines
+tags:
+  plot_type:
+    - bar
+    - stacked
+  data_type:
+    - categorical
+    - numeric
+  domain:
+    - general
+    - business
+  features:
+    - stacked
+    - annotated
+    - comparison