spec: add funnel-basic specification

plots/funnel-basic/specification.md

@@ -0,0 +1,26 @@
+# funnel-basic: Basic Funnel Chart
+
+## Description
+
+A funnel chart visualizes sequential stages of a process where values progressively decrease from one stage to the next. Each stage is represented as a trapezoidal segment that narrows from top to bottom, making it easy to identify drop-offs between stages. This chart is ideal for tracking conversion rates, sales pipelines, and multi-step processes where understanding stage-to-stage transitions is critical.
+
+## Applications
+
+- Marketing teams tracking website visitor conversion from awareness through purchase
+- Sales organizations visualizing pipeline stages from leads to closed deals
+- HR departments analyzing recruitment funnel from applications to hires
+- E-commerce platforms monitoring checkout abandonment at each step
+
+## Data
+
+- `stage` (string) - Name of each sequential stage in the process
+- `value` (numeric) - Count or amount at each stage, typically decreasing
+- Size: 3-8 stages (too many stages reduce readability)
+- Example: Sales funnel with stages ["Awareness", "Interest", "Consideration", "Intent", "Purchase"] and values [1000, 600, 400, 200, 100]
+
+## Notes
+
+- Stages should be ordered from largest (top) to smallest (bottom)
+- Use distinct colors for each stage to improve visual differentiation
+- Include value or percentage labels on each segment for clarity
+- The width of each segment should be proportional to its value relative to the first stage

plots/funnel-basic/specification.yaml

@@ -0,0 +1,30 @@
+# Specification-level metadata for funnel-basic
+# Auto-synced to PostgreSQL on push to main
+
+spec_id: funnel-basic
+title: Basic Funnel Chart
+
+# Specification tracking
+created: 2025-12-14T12:09:21Z
+issue: 789
+suggested: MarkusNeusinger
+history: []
+
+# Classification tags (applies to all library implementations)
+tags:
+  plot_type:
+    - funnel
+    - proportional
+  domain:
+    - business
+    - marketing
+    - sales
+  features:
+    - basic
+    - sequential
+    - conversion
+  audience:
+    - beginner
+  data_type:
+    - categorical
+    - numeric