fix: ProviderFactory uses `any` type — bypasses type checking

## Description

`provider-registry.ts:29` uses an `any` type that silently disables type checking for provider factory functions. Mismatched provider configs can be passed without compile-time errors.

## Location

`packages/core/src/l0/provider-registry.ts:29`

## Expected Fix

Replace `any` with the appropriate union type or a generic constraint. At minimum, use `unknown` and add a type guard.