Read the audit as a chain of labels that must all point to the same protected
word. In this pinned stabilizer toy model, the code source starts at 111, the
syndrome 11 names the repair row for error word 101, and the correction closes
back to 111; real syndrome chains also carry readout and calibration errors.
A stabilizer audit is a source-ref chain, not a final caption. Exact arithmetic here means exact results for the stated model inputs; measured inputs still carry uncertainty and significant-figure limits.