Raspberry Pi Pico Button Debounce: IRQ vs Software Polling (GP5 + GP4)

Press a button once, code counts 3-4? That is **contact bounce** — metal contacts oscillate for microseconds! 🔁 Compare 2 counting methods side-by-side in Serial: **RAW polling** (catches bounce, over-counts) vs **IRQ + software debounce** (accurate). Learn contact bounce physics, software debounce (`ticks_diff() > 50ms`), **Pin.irq()** interrupt registration, **IRQ_FALLING** trigger, ISR handlers, `global` + ISR safety. LED toggles via IRQ (visual feedback). Serial shows both counters per press