Polishing Macro Threads UI

I recorded this video to demonstrate and test a new UX for the Threads view, fixing the auto‑scroll to the bottom, oversized header, misaligned dates, and low‑contrast gray that make the current interface hard to scan. After Tio asked me to make it feel more like Superhuman, I merged patterns from Superhuman, Notion Mail, and Gmail. I introduced a collapsible header that can be scrolled away while keeping context, refined keyboard handling so Enter sends without unwanted scrolling, and right‑aligned dates with hover details. Automatic page scrolling was removed, letting users see a snippet of the thread and choose to read the full context or reply. One minor bug remains; I will submit a PR and welcome feedback on further improvements.