feat: AI architecture and implementation docs

[c-lamoureux]

Description

.claude/architecture.md:
system architecture reference covering the full pipeline, three-type pattern, VegaChart render cycle, signal system, data sources, scale system, interactive mark wiring, sanitize gate, encoding conventions, S2 parity, and file creation rules

.claude/commands/implement-new-prop.md:
skill for adding props to existing components

.claude/commands/implement-new-chart-mark.md:
skill for adding new top-level chart marks

.claude/commands/implement-new-child-component.md:
skill for adding new child components

.claude/commands/implement-bug-fix.md:
skill for diagnosing and fixing bugs

Related Issue

Motivation and Context

These are intended to create a baseline that we can build on and tweak over time. Not meant to be exhaustive or perfectly precise.

How Has This Been Tested?

Screenshots (if appropriate):

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• I have signed the Adobe Open Source CLA.
• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I have read the CONTRIBUTING document.
• I have added tests to cover my changes.
• All new and existing tests passed.

[sonarqubecloud]

Quality Gate passed

Issues
0 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud

[github-actions]

🎨 Storybook -> https://opensource.adobe.com/react-spectrum-charts/PR-768

📚 Docs -> https://opensource.adobe.com/react-spectrum-charts/PR-768-docs/