Trace character corruption through a pipeline

Inputs: [INPUT SAMPLE], [PIPELINE STEPS], [EXPECTED OUTPUT]. Identify each decode, transform, storage and render boundary. Use code points and byte observations from supplied samples to narrow the first corruption point. Output: A boundary table, minimal reproduction and test proposal. Check: The fix addresses the first bad boundary, not merely the displayed symptom. If essential information is missing, identify it rather than filling the gap with a guess. Show the first boundary where observed bytes diverge from the expected encoding.