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/html_state.rs

@@ -2,10 +2,7 @@ use common::storage::types::conversation::SidebarConversation;
 use common::storage::{db::SurrealDbClient, store::StorageManager};
 use common::utils::embedding::EmbeddingProvider;
 use common::utils::template_engine::{ProvidesTemplateEngine, TemplateEngine};
-use common::{
-    create_template_engine, storage::db::ProvidesDb,
-    utils::config::{AppConfig, RetrievalStrategy},
-};
+use common::{create_template_engine, storage::db::ProvidesDb, utils::config::AppConfig};
 use retrieval_pipeline::reranking::RerankerPool;
 use std::collections::HashMap;
 use std::sync::{
@@ -75,10 +72,6 @@ impl HtmlState {
         }
     }
 
-    pub fn retrieval_strategy(&self) -> RetrievalStrategy {
-        self.config.resolved_retrieval_strategy()
-    }
-
     pub async fn get_cached_conversation_archive(
         &self,
         user_id: &str,