Fixed
- Scroll-to-bottom cut off on new root messages — root messages have \content-visibility: auto\ applied for performance, which causes the browser to estimate their off-screen height at 64 px instead of the real ~80–120 px. _scrollToBottom\ was reading \scrollHeight\ with the underestimate and landing short. Newly appended root messages are now forced to \content-visibility: visible\ before the scroll so the real height is used immediately.
- Channel / DM switch landing at wrong scroll position — switching channels rendered up to 100 messages with \content-visibility\ height estimates, then fired a single
equestAnimationFrame\ correction that was too early. \scrollHeight\ kept shifting as estimates resolved across subsequent frames. The last 15 messages in the rendered batch are now forced visible before the initial scroll, and _scrollToBottom\ loops up to 8 animation frames until \scrollHeight\ stabilises.