* fix(whatsapp): setting systemPrompt to "" suppresses the wildcard instead of falling through to it
* test(whatsapp): reset mocks instead of only clearing call history
* docs(changelog): note WhatsApp empty systemPrompt suppresses wildcard
* test(whatsapp): preserve real module exports in process-message mocks
* test(whatsapp): whitespace-only systemPrompt also suppresses wildcard
---------
Co-authored-by: Omar Shahine <10343873+omarshahine@users.noreply.github.com>