spec(service-credential-tester): add design
8 decisions: TestResult dataclass, test_callable(store, config, secrets),
translate_connection_error shared helper (extracts test_machine_ssh patterns),
POST /api/services/test validation-first, shared ServiceTestPanel component,
field-edit-clears-result, Prom test via Grafana gateway, ssh_tasks reuses
build_ssh_client. 2-slice plan. Source findings: edit dialog is in Settings.tsx
ServiceConfigEditor (not ServicePage.tsx — spec drift); test_machine_ssh is
inlined in router (not reusable as-is).
Developer
1fc3127b58