fix: look up local declarations in environments built by `ofKernelEnv`

This PR makes a kernel error message print declarations of the current module the way they are printed everywhere else, with implicit arguments hidden, where a constant it could not resolve was previously shown fully applied.

`findAsync?` consults the imports and then `asyncConsts`, where an elaborator environment keeps the current module's own declarations. An environment built by `ofKernelEnv` keeps them in the second stage of the kernel environment's constant map instead, which neither lookup reads, so every one of them looked undefined. `findAsyncCore?` and `findTaskCore` now fall back to that stage, which an elaborator environment leaves empty, so nothing else is affected. `enableRealizationsForImports` factors the initialization of `importRealizationCtx?` out of `importModules`, the operation that field's documentation already names, so that such an environment can be given a realization context of its own.

Co-Authored-By: Claude <noreply@anthropic.com>