fix: skip Solana wallet standard registration when Metamask extension exists

[ffmcgee725]

Explanation

When both the MetaMask extension and SDK are present, registering the SDK wallet would create a duplicate "MetaMask" entry in wallet adapters, confusing users. This change ensures only one MetaMask wallet appears in the wallet selection UI.

This PR brings back the change from #164 to prevent duplicate wallet registration when the MetaMask browser extension is already installed and registered in the Solana wallet-standard registry.

References

• Fixes https://consensyssoftware.atlassian.net/browse/WAPI-1083

Checklist

• I've updated the test suite for new or updated code as appropriate
• I've updated documentation (JSDoc, Markdown, etc.) for new or updated code as appropriate
• I've communicated my changes to consumers by updating changelogs for packages I've changed, highlighting breaking changes as necessary
• I've prepared draft pull requests for clients and consumer packages to resolve any breaking changes