feat(bd-1ksf): wire hybrid search (FTS5 + vector + RRF) to CLI

Make run_search async, replace hardcoded lexical mode with SearchMode::parse(),
wire search_hybrid() with OllamaClient for semantic/hybrid modes, graceful
degradation when Ollama unavailable.

Closes: bd-1ksf

src/main.rs

@@ -1778,7 +1778,8 @@ async fn handle_search(
         fts_mode,
         &args.mode,
         explain,
-    )?;
+    )
+    .await?;
     let elapsed_ms = start.elapsed().as_millis() as u64;
 
     if robot_mode {