add ft to terminal provider

Author: nickjvandyke

lua/opencode/provider/terminal.lua

@@ -48,6 +48,7 @@ function Terminal:start()
 
     self.bufnr = vim.api.nvim_create_buf(true, false)
     self.winid = vim.api.nvim_open_win(self.bufnr, true, self.opts)
+    vim.api.nvim_set_option_value("filetype", "opencode_terminal", { buf = self.bufnr })
 
     -- Redraw terminal buffer on initial render.
     -- Fixes empty columns on the right side.