fix: multichain cold start issue with RPCClient

[elribonazo]

Explanation

The issue happens because the multichain-api-client is getting the session for the first RPC request that we run, this affects the user experience forcing the user to go back to the Dapp until the session is delivered.

I've replaced usage in RPCClient from this.provider to this.transport which does not trigger this extra RPC request.

This also makes the use of this.provider in multichain, no longer needed. We're basically using all the transport stuff from multichain-api-client but not the provider itself, not even for default transports now.

For the previous, I'd propose to create a separate PR to remove provider from the SDK and just use transports but will require a bunch of tests to be re-visited

References

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 highlighted breaking changes using the "BREAKING" category above as appropriate

---

Note

RPC calls now use transport.request (not provider) and invocation starts before opening the deeplink; tests updated accordingly.

• MultichainSDK:
  • invokeMethod now instantiates RPCClient with transport and starts invokeMethod before opening the deeplink when secure && !preferDesktop; returns the invoke promise.
• RPCClient:
  • Accepts ExtendedTransport instead of provider; redirects write/personal methods via transport.request using wallet_invokeMethod, returning response.result and handling response.error.
  • Read-only flow via HTTP unchanged (Infura/custom RPC handling, headers, parsing, errors).
• Tests:
  • Updated to mock transport.request and expectations for redirect/fallback paths; retain fetch-based assertions for readonly cases.

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[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 74.99%. Comparing base (ac8f8c3) to head (90a2ca8).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1355   +/-   ##
=======================================
  Coverage   74.99%   74.99%           
=======================================
  Files         184      184           
  Lines        4519     4519           
  Branches     1108     1108           
=======================================
  Hits         3389     3389           
  Misses       1130     1130           

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[sonarqubecloud]

Quality Gate passed

Issues
3 New issues
0 Accepted issues

Measures
0 Security Hotspots
0.0% Coverage on New Code
0.0% Duplication on New Code

See analysis details on SonarQube Cloud