feat: support Radicle as canonical workspace org

[HexaField]

Summary

• treat Radicle as the canonical remote when discovering workspace org remotes
• update server-side discovery logic and related tests
• add a spec describing the intended canonical-org behaviour

Verification

• pnpm --filter @sovereign/server test -- --run packages/server/src/remotes/discovery.test.ts packages/server/src/orgs/orgs.test.ts packages/server/src/drafts/routes.test.ts
• pnpm --filter @sovereign/server check