[sean0407]

Issue

Fixes #799.

Reproduction

With the default text encoding simulated as cp1252, reading UTF-8 YAML containing café returns café. Reading an unattend.xml containing a valid UTF-8 combining acute accent raises UnicodeDecodeError because byte 0x81 is undefined in cp1252.

Changes

• Read configuration YAML explicitly as UTF-8.
• Read and write unattend.xml explicitly as UTF-8.
• Add regression coverage for both paths with cp1252 simulated as the default encoding.

Verification

In an isolated Python 3.13.16 Docker container with networking disabled and read-only source mounts:

• python -m glazier.lib.actions.sysprep_test — 4 tests passed.
• python -m glazier.lib.config.files_test — 5 tests passed.
• The new regression tests failed against the unmodified source with the reported mojibake and UnicodeDecodeError, then passed with this change.
• git diff HEAD^ HEAD --check passed.
• Patch policy accepted 3 text files, 43 changed lines, and no binary changes.