feat(transport): add MessageChannel transport backend with transferable objects

[hristoterezov]

Summary

• Adds a new MessageChannelTransportBackend that uses the MessageChannel API for communication between windows, providing a more efficient and secure alternative to the existing postMessage-based backend.
• Extends the transport layer (Transport.ts, ITransportBackend) to support the Transferable objects pattern, enabling zero-copy transfer of ArrayBuffer, MessagePort, and other transferable types across window boundaries.
• The new backend supports scoped channel initialization, allowing multiple independent channels on the same window.

Test plan

• Verify MessageChannelTransportBackend can establish a channel between two windows (creator and receiver sides)
• Verify sendEvent with transferable objects transfers ownership correctly
• Verify request/response callbacks pass transferable objects through
• Verify dispose() properly cleans up ports and event listeners
• Verify scoped channels don't interfere with each other
• Run npm run build to ensure TypeScript compilation succeeds
• Run npm test to ensure no regressions
• Run npm run lint to ensure no linting errors

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 100.00%. Comparing base (b9b2430) to head (142f9c7).

Additional details and impacted files

@@            Coverage Diff            @@
##            master      #126   +/-   ##
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  Coverage   100.00%   100.00%           
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  Files            7         7           
  Lines         1870      1870           
  Branches        47        47           
=========================================
  Hits          1870      1870           

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