Fix the cause, not the symptom

Fix discipline. When you find the line, the fix is usually one token — but three rules keep the fix honest:

• Fix the cause, not the symptom. If the streak counter never resets, the bug is the missing else — not a clamping if stapled at the end. Symptom fixes pass the given example and fail the hidden ones.
• Re-run the WHOLE test set, not just the failing case. A fix that repairs case 3 and breaks case 1 traded one bug for another. The graded challenges here re-run everything.
• Say the one-sentence correction: "the loop must run while i + k <= length, not i + k < length." If you cannot say the sentence, you have not found the bug — you have found a symptom.

This module's broken solutions each hide exactly one bug; your fixed version must pass ALL tests including the boundary ones the original author forgot.