fix: satisfy raycast store validation

[suregoodru]

Summary

• fix TypeScript errors reported by the Raycast Store build
• replace an unavailable Raycast icon with Icon.List
• center Store screenshots with padding accepted by the upstream metadata validator

Verification

• npm test (64 tests)
• npx tsc --noEmit
• ESLint and Prettier for changed TypeScript files
• npm run build
• upstream Raycast metadata validator (3/3 images)

Notes

• No API keys, private selected text, customer data, or generated evaluation reports are included.