Cometail 0.1.0

First release, so everything the applet does is listed here.

Added

• Panel icon reflecting Tailscale connection state, with a coloured status dot
  and a shape that changes as well, so state is readable without relying on
  colour.
• Popup listing tailnet devices with name, Tailscale address, OS and online
  status, online devices first.
• Connect and disconnect, via tailscale up and tailscale down.
• Copy a device's Tailscale address, or its MagicDNS name via the DNS button.
  The MagicDNS button is hidden when the tailnet has MagicDNS disabled.
• Exit node selection, and an explanation in place of an empty dropdown when no
  device on the tailnet advertises itself as one.
• Toggle for accepting the tailnet's DNS configuration.
• Explicit diagnostics when tailscaled refuses a command, naming
  sudo tailscale set --operator=$USER rather than failing silently.
• Sign-in button that hands the auth URL to the browser when the daemon is
  logged out.
• Change notifications from the LocalAPI event bus at
  /localapi/v0/watch-ipn-bus, so the panel reacts immediately. Falls back to
  polling every 5 s when the socket is unreachable.
• just reload and just dev for restarting the applet in a running panel.

Notes

• libcosmic is pinned to the revision COSMIC 1.5.0 was built against.
• Device data comes from tailscale status --json rather than the event bus's
  netmap, deliberately, to avoid re-deriving Online and ExitNodeOption from
  the daemon's internal representation.