Review and improve obvious/easy-to-spot wrong answers

[rostik36]

Audit all 150 quiz questions for wrong answer options that are too obvious or easy to spot. Replace with subtle, realistic bugs that require careful reading.

Examples:

• Q63: Replaced 'From Beginning' (obvious) with 'Off-by-One Stop' (subtle)
• Q58: Replaced 'Interleave + Sum' (confusing) with 'Simultaneous Walk (Wrong Carry)' (subtle)

Goal: Make every wrong answer a realistic mistake that students might actually make.