fix: prevent CRLF translation in stdio_server on Windows

[Epochex]

Fixes #2433.

On Windows, TextIOWrapper defaults to newline=None and translates \n -> \r\n on output. stdio_server wraps sys.stdout.buffer with TextIOWrapper, so every JSON-RPC message was emitted with CRLF line endings.

This sets newline= on the stdio stdin/stdout wrappers to disable platform newline translation and keep LF-delimited NDJSON.

Tests:

• uv run --frozen pytest tests/server/test_stdio.py

[yyzquwu]

I ran an independent Windows-focused repro packet from Agent Windows Lab and it supports the direction of this PR.

Environment/evidence:

• Windows 11 10.0.26200, Python 3.13.13
• stdio_newline_framing: Python text-mode stdout emitted CRLF (0d0a) while binary stdout emitted LF (0a)
• mcp_stdio_jsonrpc_probe: binary stdio round-tripped an MCP-style JSON-RPC initialize message with LF framing
• The generated report was redacted and passed the redaction verifier

Command used:

python .\scripts\run_agent_windows_lab.py --out .\artifacts\issue-packet --case mcp --issue-target modelcontextprotocol-python-sdk
python .\scripts\verify_redacted_report.py .\artifacts\issue-packet\agent-windows-lab-report.json

Public harness commit: yyzquwu/agent-windows-lab@ab5e714
Windows proof run: https://github.com/yyzquwu/agent-windows-lab/actions/runs/26735979548

This gives independent Windows evidence for treating stdio framing as byte-level transport behavior and preventing text-mode newline translation from leaking into JSON-RPC framing.

[Kludex]

You've opened a duplicated pull request, please search opened PRs before creating new ones. Duplicated from #2552.