Refactor: Real MemoryStore replaces Mocks

Multiple tests across goal signal, adaptive layer, and onboarding integrations have been refactored to use real MemoryStore instances instead of mocking infrastructure calls. This shifts assertions from mock call history to verifying actual store state, such as key existence.

• Converted mock instances in goal signal service tests to use MemoryStore and assert on store state.

• Converted mock instances in adaptive layer service tests to use MemoryStore.

• Converted mock store helpers in onboarding nudge tests to use a pre-populated MemoryStore.