test: fix WithICDelta fake dropping supplied delta

[aheritier]

Problem

pkg/a2a/adapter_run_test.go defines a WithICDelta fake that silently discards the supplied delta instead of applying it like WithContext (or failing loudly). This can make adapter tests pass without exercising the requested state change.

Scope

• Make the fake apply the delta consistently with WithContext, or fail loudly when unsupported.
• Add a regression test covering the supplied delta.