adjust starcoder model stop tokens

matching what the continue.dev plugin code specifies for this. seems
to work ok (but starcoder still seems poor overall)

nvim/lua/plugins/nvim-cmp.lua

@@ -48,7 +48,7 @@ return {
             elseif model:match '^qwen' then
               return { '<|endoftext|>' }
             elseif model:match '^starcoder' then
-              return { '<file_sep>', '<|end_of_text|>', '<|endoftext|>' }
+              return { '<fim_prefix>', '<fim_suffix>', '<fim_middle>', '<file_sep>', '<|endoftext|>' }
             elseif model:match '^codestral' then
               return { '[INST]', '[/INST]', '[PREFIX]', '[MIDDLE]', '[SUFFIX]' }
             elseif model:match '^deepseek%-coder' then