feat: add data-viz skill for data storytelling and visualizations

[arora-saurabh448]

Summary

• Adds a new data-viz skill for data storytelling and visualization/data products
• Renames skill from previous name to data-viz for consistency
• Includes comprehensive skill definition (SKILL.md) and a component guide reference (component-guide.md)

Changes

• .opencode/skills/data-viz/SKILL.md — new skill definition with prompts and usage guidance
• .opencode/skills/data-viz/references/component-guide.md — reference guide for visualization components (994 lines)

Test plan

• Run through a sample visualization request to confirm skill output is coherent
• Confirm no regressions in existing skills

🤖 Generated with Claude Code

[sentry]

Bug: The code example for KPI aggregation uses _.maxBy(data, "revenue"), which returns an object, not the maximum numeric value as implied.
_{Severity: MEDIUM}

Suggested Fix

Update the code example to correctly extract the numeric value from the object returned by _.maxBy. For instance, change max: _.maxBy(data, "revenue") to max: _.maxBy(data, "revenue")?.revenue or use an alternative like _.max(_.map(data, 'revenue')).

Prompt for AI Agent

Review the code at the location below. A potential bug has been identified by an AI
agent.
Verify if this is a real issue. If it is, propose a fix; if not, explain why it's not
valid.

Location: .opencode/skills/data-viz/references/component-guide.md#L263

Potential issue: The code example in `component-guide.md` for calculating KPIs uses
`_.maxBy(data, "revenue")` to find the maximum revenue. This function returns the entire
data object containing the maximum value, not the numeric value itself. If an AI agent
copies this example to generate code, any subsequent attempt to use the result as a
number (e.g., for mathematical operations or formatting) will fail, potentially leading
to incorrect outputs like `[object Object]` or runtime errors in the AI-generated code.

_{Did we get this right? 👍 / 👎 to inform future reviews.}