Twin modules: <feature> and <feature>-empty

Two modules, same package, same declarations. One wraps the real integration; the other returns values that make every caller take the "not available" path without knowing there is one.

// adapted — <feature>-empty/src/…/<Feature>.kt
package com.example.app.<feature>

// STUB build: <feature> is not available. Every function is a safe no-op so callers
// never branch on the build.

fun init<Feature>(context: Context): Boolean {
    Logger.d(TAG, UNAVAILABLE)
    return false
}

fun is<Feature>Available(): Boolean = false