test(build-context): read the nested OMS fixture without newline translation

[MohammedAlkindi]

test_build_context_scans_nested_oms_signature fails on Windows and passes on Linux.

The fixture is written byte-exact, so it keeps its CRLF endings and build_context caches it verbatim. The assertion compared that against Path.read_text(), which applies universal-newline translation and returns LF, so the two never match on Windows.

Reading the fixture back as bytes and decoding matches how it is written. Path.read_text(newline="") would also work, but that parameter is 3.13+ and pyproject.toml sets requires-python = ">=3.12,<3.15".

Measured on Windows 11, uv-managed CPython 3.14.0, -p no:randomly:

before  1 failed   AssertionError: '...}}\r\n' == '...}}\n'
after   1 passed

Verified in the full-file run as well, not only in isolation. Also verified on top of #505, which fixes the write side of the same file: this change is independent of it and both orderings pass.

The other failures in this file on Windows are unrelated. #501, #502 and #503 cover the symlink, FIFO and secure-open cases; the remaining two are timing-sensitive and flake on main as well.

[MohammedAlkindi]

Where this sits relative to the other open Windows test PRs, since it is the last of the set.

With #501, #502, #503, #505 and this one applied together, tests/nodes/test_build_context.py goes from 12 failures on main to 0 on Windows 11. Three runs of the stack: 72 passed, 8 skipped once, and 71 passed, 1 failed twice.

The one intermittent failure is test_dense_directory_discovery_and_cache_complete_with_modest_real_elapsed_time, which is load-sensitive and fails on main too, 1 of 3 runs there. Nothing in this PR touches it.

The 8 skips are the symlink and FIFO cases from #501 and #502, which cannot run without elevation or Developer Mode.

[rng1995]

[SkillSpector Review]

Reviewed head 3cd47535cdec5116e3259a18f1aa1148da13805b — APPROVE.

The assertion now compares the exact decoded fixture bytes against the byte-faithful cache, avoiding Windows universal-newline normalization while preserving the production contract. This is a focused and portable test correction with no required changes.

Required checks pass, but GitHub currently reports mergeStateStatus=BEHIND; update against current main and re-run required checks before merging.

[rng1995]

[SkillSpector Review]

Re-reviewed current head b6c2d9fc39087df572fe936fba07fe7b484f8e57. The current PR delta remains the byte-faithful fixture assertion; intervening changes in the file come from unrelated main symlink-portability work. read_bytes().decode("utf-8") correctly avoids Windows universal-newline translation while retaining Python 3.12 compatibility. I found no required change.

All required checks pass, but GitHub reports mergeStateStatus=BEHIND; update and revalidate before merging.