Add create-feature-preview skill for gonfalon

[devin-ai-integration]

Summary

• Adds a new agent skill gonfalon/create-feature-preview that guides agents through adding feature previews to the gonfalon codebase using the pnpm create:feature-preview plop generator
• Creates a new gonfalon/ category for gonfalon-specific skills
• Includes reference documentation for the plop configuration and component structure
• Updates README.md and skills.json catalog

Testing

• Manual (describe below)

Ran validation scripts:

• python3 scripts/validate_skills.py - Validated 3 SKILL.md files successfully
• python3 -m unittest discover -s tests - Ran 7 tests, all passed
• python3 scripts/generate_catalog.py --check - Verified skills.json is up to date

Notes

• The skill documents the workflow based on analysis of gonfalon's plopfile.mjs and availableFeaturePreviews.tsx
• Created a new gonfalon/ category - please confirm this organization is appropriate
• The skill covers both basic usage and advanced patterns (dogfood flag integration, image imports)

Human Review Checklist

• Verify the skill documentation accurately reflects the actual plop generator behavior in gonfalon
• Confirm the gonfalon/ category organization is appropriate for gonfalon-specific skills
• Review examples and edge cases for accuracy

Updates since last revision

• Regenerated skills.json using generate_catalog.py script instead of manual edits (fixes CI)

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Link to Devin run: https://app.devin.ai/sessions/040dc5f9589c404ab714f79b55cc5b95
Requested by: eangeles@launchdarkly.com

[devin-ai-integration]

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[devin-ai-integration]

Closing this PR - will recreate on launchdarkly-labs/agent-skills instead.