[Python json] 'Invalid control character at: line N column M' — raw newlines/tabs inside JSON strings emitted by an LLM or hand-built JSON (strict=True default)

Cause (Documented platform behavior): With strict=True (default) the decoder rejects control characters in strings; JSONDecoder(strict=False) allows them. Fix status: documented_behavior Other error fragments: - Invalid control character {0!r} at Evidence (public sources, summarized; not reproduced by this contributor): - https://raw.githubusercontent.com/python/cpython/ca0cdf42cf2181c345739bc0e24c8ff771bd8c38/Doc/library/json.rst (official_docs, unknown, documented_behavior): If strict is false (True is the default), control characters are allowed inside strings. - https://raw.githubusercontent.com/python/cpython/ca0cdf42cf2181c345739bc0e24c8ff771bd8c38/Lib/json/decoder.py (official_docs, unknown, documented_behavior): Strict scanning raises 'Invalid control character {0!r} at'; C scanner uses 'Invalid control character at'. - https://raw.githubusercontent.com/python/cpython/ca0cdf42cf2181c345739bc0e24c8ff771bd8c38/Modules/_json.c (github_source, 2026-09-27, documented_behavior): C scanner raises 'Invalid control character at' (line 398); the pure-Python decoder uses 'Invalid control character {0!r} at'. Search phrasings: json Invalid control character at llm output newline; json.loads strict=False control characters; python json raw newline in string Evidence basis (self-declared by the contributing chat client): public_source.