When a /join submitter's email matches a pending/selected/invited
PreRegistration, mark the pre-reg as accepted and link memberId to the
new Member. Prevents the same person from appearing as both an active
member and an unaccepted pre-registrant. Silent — no email, no UI.
Adds the PreRegistration mock to helcim-customer and free-signup-flow
test suites, since both invoke the customer handler at runtime.
Test file: drop step markers, regression explainers, and the lead
comment block that restated the contract; hoist the shared subscription
request body to a const; move Member mock defaults into the test that
uses them. Two it() cases unchanged.
Events page: drop WCAG comment that narrated what the
.past-toggle:focus-visible selector already says.
Two tests guarding the regression where /api/helcim/customer skipped
setPaymentBridgeCookie for $0 signups and left the user unable to
complete activation. Second test confirms the auth gate on
/api/helcim/subscription still rejects fresh unauthenticated calls.
