scripts/repo_shape.py load_yaml catches OSError and YamlError but not UnicodeDecodeError, so a plan or manifest holding a non-UTF-8 byte makes adopt-project.py check and execute exit 1 with a traceback instead of REFUSED yaml-unreadable #192

(lane openRepoShape-2, 2026-10-09T08:57:19Z) Found by this lane's review of PR #187 (#169) at 8a542bd (its N2); pre-existing on main 21f5c33 and outside #169's region (scripts/repo_shape.py). Not claimed.

What is wrong. scripts/repo_shape.py:624-632 load_yaml catches OSError around read_text(encoding="utf-8") and YamlError around the parse, but not UnicodeDecodeError. A YAML file holding a byte that is not UTF-8 (a raw 0xff inside a leg path of an adoption plan, in the probe; any manifest, pin or plan the tools read is the same path) therefore escapes as a Python traceback:

adopt-project.py check --plan adoption-plan.yaml     # exit 1, UnicodeDecodeError traceback, no FINDING line
adopt-project.py execute --plan adoption-plan.yaml   # exit 1, same traceback, no REFUSED line

No leg repository is created, so nothing is damaged; but the contract is that an unreadable input is a REFUSED yaml-unreadable line with a remediation, exit 2, the way an unreadable file or an unparsable one already is. plan itself refuses the value on its alphabet (#169 / PR #187), so the file reaches this state only by hand-editing or a foreign writer, which is what check is for.

Fix. Catch UnicodeDecodeError with OSError in load_yaml and raise Refusal("yaml-unreadable", f"{path}: not UTF-8 at byte {exc.start}", "Remediation: ..."); one test per reader that goes through it (check, execute, the doctor, validate-manifest.py). Driver: opensoft/brett-wip handoffs/xFactory/attachments/lane-openRepoShape-2/review187-8a542bd/tools/matrix.py (row b-non-utf8).