Defer need-check-nil and clean up stale suppressions

emmylua deserialises an unknown diagnostic code to a catch all that
matches no checker, so every `invisible`, `nil-check` and
`global-element` suppression was silently doing nothing. Renamed to the
emmylua codes. `name-style-check` has no equivalent and is dropped, it
was already disabled under luals.

The `get_tile` suppressions referenced an api typedef bug from 2024
which no longer reproduces.

need-check-nil is deferred rather than disabled on merit: a third of the
407 findings come from MapPosition and BoundingBox being aliased as
`struct|[double, double]`, so every `entity.position.x` reads as
possibly nil. The rest need per site knowledge of runtime invariants.

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

exp_groups/module/globals.lua

@@ -5,7 +5,7 @@ Therefore, we advise that this should be the only file in your module to expose
 Typically this would be your control file as shown in the example below
 ]]
 
---- @diagnostic disable: global-element
+--- @diagnostic disable: global-in-non-module
 
 -- Access using `/sc exp_groups.foo()`
 exp_groups = require("modules/exp_groups/control")