docs: document wdk-wallet-solana beta.6-beta.7 release changes

Created by: ihsraham

Summary

• document the public docs updates for @tetherto/wdk-wallet-solana v1.0.0-beta.6
• update the same docs for @tetherto/wdk-wallet-solana v1.0.0-beta.7 after the published typings caught up with the beta.6 runtime behavior
• add changelog entries for April 15, 2026 and April 19, 2026

Documentation Fixes

• document runtime failover support for ordered rpcUrl lists plus retries
• update Solana derivation guidance to use hardened SLIP-0010 child paths in the overview, configuration, API, and account management docs
• document TransactionMessage lifetime handling and explicit fee-payer validation for custom transaction flows
• fix stale SOL transfer examples to use to and remove an unsupported extra transfer() argument in the token transfer guide
• remove the temporary beta.6 typing caveat now that beta.7 publishes SolanaWalletConfig.rpcUrl as string | string[]

Changelog Updates

• April 15, 2026: wallet-solana v1.0.0-beta.6
• April 19, 2026: wallet-solana v1.0.0-beta.7

Release References

• Release PR: https://github.com/tetherto/wdk-wallet-solana/pull/53
• Release PR: https://github.com/tetherto/wdk-wallet-solana/pull/55
• npm package: https://www.npmjs.com/package/@tetherto/wdk-wallet-solana/v/1.0.0-beta.6
• npm package: https://www.npmjs.com/package/@tetherto/wdk-wallet-solana/v/1.0.0-beta.7

Validation

• git diff --check
• TypeScript probe for the documented typed API paths in beta.6
• TypeScript probe for the published rpcUrl: string | string[] typing in beta.7
• Verified changelog dates from npm publish timestamps because there are no GitHub release objects for these Solana versions