feat: support anchor and program metadata IDL sources

[dev-jodee]

Summary

• parse and persist idlSource from the URL and API fetch flow
• add program-metadata IDL fetching alongside the existing Anchor path
• support auto source selection by comparing latest update timestamps and preferring PMP on ties
• add coverage for explicit sources, auto selection, fallback, and URL parsing

Testing

• npm test
• npx eslint app/page.tsx app/api/fetch-idl/route.ts lib/fetch-idl.ts lib/idl-source.ts

[vercel]

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Project	Deployment	Actions	Updated (UTC)
castaway	Ready	Preview, Comment	Mar 26, 2026 1:13pm