Buzz Desktop v0.4.9

• Restyle onboarding: branded landing screen, yellow/gradient backgrounds, new starter avatars (#1982) (831c80c1a)
• Guide CLI installation and subscription sign-in (#1980) (8d3666c5f)
• unify channel add + search into one entry point (#1964) (3dd236eb6)
• Apply optional relay join policy across join flows (#1894) (6c2d66757)
• fix(desktop): preserve relaunch through mesh shutdown (#1966) (a1626f96c)
• Persist agent audiences with native inline mentions (#1949) (19dc33bda)