spec: add funnel-basic specification

[github-actions]

New Specification: funnel-basic

Closes #789

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specification.md

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

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Next: Add approved label to the issue to merge this PR.

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🤖 spec-create workflow