I built a share button that doesn't assume where...

The problem I'm on Blacksky. Every "Share to Bluesky" button I hit sends people to bsky.app — not where I actually am. If you're on deck.blue, Langit, or any other AT Protocol client, those buttons don't work for you either. Same problem on the Fediverse — "Share to Mastodon" assumes you're on mastodon.social. The open social web has 12+ AT Protocol clients and counting, thousands of Mastodon instances, and growing. But every share button hardcodes a single destination. Nobody had built the fix.