Parse error messages embedded the entire first line of a value, so a single malformed escape could copy a neighbouring secret verbatim into logs; the context is now capped at eighty bytes without splitting a UTF-8 character, using plain byte operations so the formatter cannot call an mbstring function the polyfill does not provide, and control bytes in the reported context are escaped so log lines stay printable. A malformed pattern passed to allowedRegexValues reported every value as a mismatch instead of the compile failure, the empty-file-path message blamed the path when the names list was empty, and the repository builder's error text and doc comments were inaccurate; these are corrected. Encoding names are now matched case-insensitively and through their aliases. A new tests workflow job runs the suite with the mbstring functions the polyfill does not implement disabled, so any future use of one fails in CI rather than only on installs that rely on the polyfill. This is stacked on #606.