fix(cli): handle unencodable search results

[shixi-li]

Summary

• fall back to replacement characters when search result metadata or content cannot be encoded by the console
• preserve text that the active console encoding supports
• cover file paths and result content with a strict GBK output regression

Addresses the GBK console-output failure described in #166. The separate stale-daemon environment problem remains out of scope.

Testing

• .venv/bin/python -m pytest tests/test_cli_helpers.py::test_print_search_results_replaces_unencodable_console_characters -q
• .venv/bin/python -m pytest tests/test_cli_helpers.py -q (25 passed)
• .venv/bin/ruff check src/cocoindex_code/cli.py tests/test_cli_helpers.py
• .venv/bin/ruff format --check src/cocoindex_code/cli.py tests/test_cli_helpers.py
• .venv/bin/python -m mypy src tests
• uv build --offline

The full developer suite is not reported as passing locally: its sentence-transformers dependency resolves to torch 2.13, which has no Intel macOS wheel. The focused CLI suite, strict static checks, offline package build, and GBK-specific regression all pass.

[georgeh0]

Thanks for the enhancement!