chore: refactor retrieval pipeline to chunk-first RRF with derived entities and slimmer eval surface.

Collapse the multi-strategy entity engine into one benchmarked chunk retrieval path, derive entities from retrieved chunks, and update consumers, docs, and clippy fixes across the workspace.

html-router/src/routes/index/handlers.rs

@@ -13,7 +13,7 @@ use crate::{
     middlewares::{
         auth_middleware::RequireUser,
         response_middleware::{
-            template_as_response, HtmlError, TemplateResponse, TemplateResult, ResponseResult,
+            template_as_response, TemplateResponse, TemplateResult, ResponseResult,
         },
     },
     utils::text_content_preview::truncate_text_contents,