Fix duplicate class and annotation placement lint errors

Classes contributed to by more than one file now carry the `partial`
attribute. trains.lua declared its command as `ExpCommand_Artillery`,
which was a copy paste.

`Color.0` and `MapPosition.0` became `.struct` in fmtk 2.1.6.

emmylua rejects `@type` on a function statement or a `do` block, so
those are moved onto the local or replaced by `@param` and `@return`.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

exp_scenario/module/control/spawn_area.lua

@@ -7,7 +7,7 @@ local config = require("modules.exp_legacy.config.spawn_area")
 --- Apply an offset to a LuaPosition
 --- @param position MapPosition
 --- @param offset MapPosition
---- @return MapPosition.0
+--- @return MapPosition.struct
 local function apply_offset(position, offset)
     return {
         x = (position.x or position[1]) + (offset.x or offset[1]),