Follow-ups from review of #3194:
- ci.yml: drop unconditional --ignore=tests/channels/test_matrix_channel.py.
That test file already calls pytest.importorskip("nio") at module top, so
it self-skips on Windows (where nio isn't installed) without also hiding
62 tests from Linux CI.
- filesystem.py: hoist `import os` to the module top and drop the duplicate
inline import in ReadFileTool.execute. Document the CRLF->LF normalization
as intentional (primarily a Windows UX fix so downstream StrReplace/Grep
match consistently regardless of where the file was written).
- test_read_enhancements.py: lock down two new behaviors
* TestFileStateHashFallback: check_read warns when content changes but
mtime is unchanged (coarse-mtime filesystems on Windows).
* TestReadFileLineEndingNormalization: ReadFileTool strips CRLF and
preserves LF-only files untouched.
- test_tool_validation.py: restore list2cmdline/shlex.quote in
test_exec_head_tail_truncation. The temp_path-based form was correct,
but dropping the quoting broke on any Windows path containing spaces
(e.g. C:\Users\John Doe\...). CI runners happen not to have spaces so
this slipped through.
Tests: 1993 passed locally.
Made-with: Cursor
