The nightly Schemathesis job failed with a schema-loading error:
'unacceptable character #x0080: control characters are not allowed'. The
served openapi.yaml contained 215 em dashes (U+2014) and box-drawing
section dividers (U+2500); Schemathesis's strict YAML parser mis-decodes
those multi-byte UTF-8 sequences as C1 control chars and refuses to load
the schema, so no fuzz checks ran. (PyYAML is lenient, which is why the
local yaml.safe_load check passed.)
Replace every non-ASCII char with ASCII '-'. This also clears an
em-dash style-rule violation. Add a docs.test.ts guard asserting the
served spec is ASCII-only, with a clear message, so this can't regress.
Pre-existing issue (the dashes predate this branch); surfaced while
verifying CI is green.
