manycode 0.5.0 - talk on the side, .env stays home

• Talk on the side. Every session now has a chat channel that never touches
  the shared prompt - coordinate who's driving without typing over each other.
  Browser joiners get a sidebar with an unread badge, CLI joiners press Ctrl-T
  to compose (Enter sends, Esc cancels), and the host chats from any terminal
  with manycode say "…" plus macOS notifications for incoming messages. Late
  joiners get recent chat replayed; sender names are stamped by the host.
• .env values don't leak by default. Hosting a folder with .env files asks
  what joiners should see. The default masks every value with •••••• in the
  live stream, the scrollback replay, and recordings - even when a secret is
  split across output chunks - while the host's own screen stays raw.
  --share-secrets opts into sharing, --redact-secrets skips the question.