docs/emitter-design: naming policy should be allowed to consult the source spelling for acronyms #717

Problem

Canonical words are lowercase: iOSVersion becomes i_os_version, HTTPServer2FA becomes http_server_2_fa. Casing those words back up gives IOsVersion and HttpServer2Fa. §4.12's Acronyms() table can fix known acronyms, but not mixed-case ones like iOS, and the rule against re-splitting cased strings is right for word boundaries.

Proposal

State that naming.Policy may consult Naming.Source to recover the casing of an acronym whose words the canonical form already fixes, never to find word boundaries. This keeps renderings like IOSVersion possible without reopening re-splitting.