refactor(stdlib): replace source any with unknown/generics

Type guards take `unknown`; walkers/comparators (get/set/isEqual) narrow via
casts; generic defaults and constraints tightened. Truly-idiomatic any-function
constraints and load-bearing type-level any are kept with explanatory comments.

core/stdlib/eslint.config.ts

@@ -1,3 +1,3 @@
-import { base, compose, imports, stylistic, typescript } from '@robonen/eslint';
+import { base, compose, imports, stylistic, tests, typescript } from '@robonen/eslint';
 
-export default compose(base, typescript, imports, stylistic);
+export default compose(base, typescript, imports, stylistic, tests);