[codex] Test encoding edge cases across request stacks

[maurosoria]

Summary

Adds regression coverage for network encoding edge cases across the sync Python, async Python, and native Rust request stacks.

Changes

• Preserve and classify malformed response/read errors more precisely in Python requesters.
• Decode text bodies with replacement instead of dropping invalid bytes silently.
• Add display-only sanitization/truncation for bidi controls, ZWJ-heavy emoji paths, redirects, and queued directories.
• Preserve raw HTTP request targets in the native backend when dot segments would otherwise be normalized by the URL layer.
• Add tests for CJK byte length, German case expansion, UTF-16 BOM artifacts, lying charset bytes, Shift-JIS backslash overlap, RTL controls, and large ZWJ emoji sequences.

Validation

• VIRTUAL_ENV=/home/mauro/dirsearch/.venv PATH=/home/mauro/dirsearch/.venv/bin:$PATH /home/mauro/dirsearch/.venv/bin/python -m maturin develop --manifest-path native/Cargo.toml
• /home/mauro/dirsearch/.venv/bin/python -m unittest tests.connection.test_response tests.connection.test_native_response tests.connection.test_requester tests.utils.test_crawl tests.utils.test_terminal
• /home/mauro/dirsearch/.venv/bin/python -m unittest discover tests
• /home/mauro/dirsearch/.venv/bin/python testing.py
• cargo test --manifest-path native/Cargo.toml
• git diff --check

Note: test_schemedet still emits existing ResourceWarnings for unclosed SSL sockets; the suite passes.