fix: default encoding_error_handler to 'replace' in StdioServerParameters

[Christian-Sidak]

Summary

stdio_client crashed with an ExceptionGroup when the child process wrote invalid UTF-8 bytes to stdout because StdioServerParameters.encoding_error_handler defaulted to "strict".

This was already fixed on the server side in PR #2302; this PR applies the same one-line fix to the client side.

Change: default encoding_error_handler from "strict" to "replace" so malformed bytes are replaced with U+FFFD, which then fails JSON parsing and is delivered as an in-stream Exception — keeping the transport alive for subsequent valid messages.

Test

Added test_stdio_client_invalid_utf8 to tests/client/test_stdio.py: spawns a child that writes b"\xff\xfe\n" followed by a valid JSON-RPC line, and asserts the first stream item is an Exception and the second is a SessionMessage.

Fixes #2454

[Christian-Sidak]

Friendly bump -- let me know if anything needs changing.

[Christian-Sidak]

Friendly bump -- let me know if anything needs changing.

[Christian-Sidak]

Fixed the CI failures: the new test exercises the except Exception as exc path in stdio_client (invalid UTF-8 is now decoded via replace handler and then fails JSON parsing), which made the # pragma: no cover annotation stale. Removed it so strict-no-cover no longer flags those lines.

[Christian-Sidak]

Fixed the coverage gap: branch 532->537 was the async-for exhaustion path, never reached because the loop always exited via break. Removed time.sleep(1) from the child script so the process exits immediately after writing the two lines, then dropped the early-break guard. The loop now terminates by exhaustion, covering both branches and restoring 100% coverage.