fix(api): custom commands with arguments

I had broken it because I didn't think it was supported. But it was :)

Author: cameronr

lua/opencode/api.lua

@@ -1231,10 +1231,10 @@ function M.get_slash_commands()
       table.insert(result, {
         slash_cmd = '/' .. name,
         desc = def.description or 'User command',
-        fn = function()
-          M.run_user_command(name, {})
+        fn = function(...)
+          M.run_user_command(name, ...)
         end,
-        args = false,
+        args = config_file.command_takes_arguments(def),
       })
     end
   end

lua/opencode/config_file.lua

@@ -126,4 +126,11 @@ function M.get_mcp_servers()
   return cfg and cfg.mcp or nil
 end
 
+---Does this opencode user command take arguments?
+---@param command OpencodeCommand
+---@return boolean
+function M.command_takes_arguments(command)
+  return command.template and command.template:find('$ARGUMENTS') ~= nil or false
+end
+
 return M

tests/unit/api_spec.lua

@@ -404,7 +404,7 @@ describe('opencode.api', function()
       config_file.get_user_commands = function()
         return {
           ['build'] = { description = 'Build the project' },
-          ['test'] = { description = 'Run tests' },
+          ['test'] = { description = 'Run tests', template = 'Run tests with $ARGUMENTS' },
         }
       end
 
@@ -423,7 +423,7 @@ describe('opencode.api', function()
           test_found = true
           assert.equal('Run tests', cmd.desc)
           assert.is_function(cmd.fn)
-          assert.falsy(cmd.args)
+          assert.truthy(cmd.args)
         end
       end