feat(mod-api): expose developer mode

src/mods/Loader.lua

@@ -980,6 +980,10 @@ function Loader:_api(mod)
     id = modId,
     version = mod.manifest.version,
     path = mod.path,
+    -- Fixed at Loader construction and copied as plain data: a sandboxed
+    -- entry chunk can decide whether to register developer-only diagnostics
+    -- without receiving the process environment or the loader itself.
+    developer = loader.dev == true,
     -- a deep copy: what a mod does to its own view never reaches the loader
     manifest = Merge.deepCopy(mod.manifest),
     content = {},