fix: avoid shared rotating logs on Windows

[he-yufeng]

Summary

• use per-process log files on Windows (kimi.<pid>.log) so concurrent CLI/web/worker processes do not rotate the same open kimi.log
• keep the existing shared kimi.log path on non-Windows platforms
• point fatal-error messages at the effective log path and keep CLI error snapshots stable across Rich box styles

To verify

• uv run pytest tests\e2e\test_cli_error_output.py tests\utils\test_logging.py -q
• uv run python -m py_compile src\kimi_cli\app.py src\kimi_cli\cli\__init__.py src\kimi_cli\utils\logging.py tests\utils\test_logging.py tests\e2e\test_cli_error_output.py
• uv run ruff check src\kimi_cli\app.py src\kimi_cli\cli\__init__.py src\kimi_cli\utils\logging.py tests\utils\test_logging.py tests\e2e\test_cli_error_output.py
• uv run ruff format --check src\kimi_cli\app.py src\kimi_cli\cli\__init__.py src\kimi_cli\utils\logging.py tests\utils\test_logging.py tests\e2e\test_cli_error_output.py
• git diff --check

Fixes #2348

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[devin-ai-integration]

✅ Devin Review: No Issues Found

Devin Review analyzed this PR and found no potential bugs to report.

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