tests: add coverage for options, types, and HTTP server
- options_test.go: GetOption, GetFloatOption, GetIntOption, GetBoolOption
with native types, JSON round-trips, missing keys, and wrong types
- types_test.go: Status JSON marshal/unmarshal (strings, legacy ints,
round-trip, unknown values), CheckTarget.Scope/String, BuildRulesInfo,
empty-ID rejection
- server_test.go: /health, /collect (success, error, bad body),
/definition, /evaluate (all rules, disabled rule), /report (HTML,
metrics, bad body), missing endpoints without CheckerDefinitionProvider