fix: preserve grouped domains on fluent routes

[elpete]

Summary

• preserve a domain supplied by group() when starting a fluent route definition
• carry the grouped domain through inline event and response route registration
• add regression coverage for both fluent and inline route forms

This is a follow-up to #690. That PR preserved domains during nested route resolution; this fixes the earlier registration step where route() processed the grouped domain but discarded it before addRoute().

Verification

• RouterTest: 67 passed, 0 failed, 0 errors on BoxLang 1.17.0+58
• targeted cfformat check for RouterTest.cfc passed
• git diff --check passed

Note: as recorded on #690, the newer local cfformat version disagrees with CI about an unchanged alignment line in Router.cfc; that unrelated line remains byte-identical to development.