opencode native 0.12.0

Added

• A terminal (Ctrl+Shift+T), a panel like the others: the shells of the server, wherever it runs, in tabs, in the folder of the session.
  Emulation is Ghostty's, through libghostty-vt: colours, styles, scrollback, what programs ask of a terminal. The keys go to the shell
  while it has the focus, Ctrl+K and Escape included; Ctrl+Shift+C and V copy and paste, the wheel goes through the history, the mouse
  selects, or goes to the program that asks for it. A shell outlives the program and comes back when the panel opens; closing its tab
  ends it.

Changed

• The dock shows only the panels that are open.
• Building needs nothing more: Zig and Ghostty, pinned, are fetched into build/vt the first time.

Windows 10 and 11 (x64): one executable; run it, or install it for your user from its Setup (title bar menu > Setup...).
Linux (x64): the archive holds one program; run it, or ./opencode-native --install (an entry in the applications menu). Needs Vulkan, libxkbcommon, fontconfig, Wayland or X11.

It finds the opencode server of the computer by itself (another one: --url, or the status bar's server menu).