[ac1982]

Related to #606.

Clarify that normalize_value_for_hashing receives individual values independently of the pairwise match() method. Normalizers must check their own type/path scope and return unrelated objects unchanged; an accidental None return can hide differences under ignore_order=True.

Update the API docstring and custom-operator guide, with numeric-list examples showing that the string normalizer preserves unrelated comparisons. Fix the prompts in the same GUID example so it can be executed as a doctest. Runtime behavior is unchanged.

Validation: all 14 doctests in the updated example pass; pytest tests/test_operators.py --cov=deepdiff passes (10 tests); Sphinx HTML build with warnings as errors passes; git diff --check passes. The complete custom-operator page has five remaining pre-existing doctest failures in other examples (eight on the unmodified baseline); a clean whole-page doctest run or full library test suite is not claimed.

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