Replace 5 copies of the ~80-line backend resolution pattern with a
single InsightGenerator::resolve_backend() builder that returns a
ResolvedBackend (chat + local clients, BackendKind enum, images_inline
flag). Tool dispatch now takes &ResolvedBackend instead of
&OllamaClient + model + backend strings.
Remove duplicated ollama/openrouter/llamacpp fields from
InsightChatService — InsightGenerator owns them and resolve_backend
uses them. Delete build_chat_clients (replaced by resolve_backend).
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
a8a661f70a