feat(grpc): handle IndexSymbols from client, index to OpenSearch

When client sends IndexSymbols after session start, Sol indexes
the symbols to the sol_code OpenSearch index. Each symbol becomes
a SymbolDocument with file_path, name, kind, signature, docstring,
branch, and source="local".

src/grpc/service.rs

@@ -159,6 +159,36 @@ async fn run_session(
                     }
                 }
             }
+            Some(client_message::Payload::IndexSymbols(idx)) => {
+                // Index client symbols to OpenSearch code index
+                if let Some(ref os) = state.opensearch {
+                    let index_name = state.code_index_name();
+                    let mut indexer = crate::code_index::indexer::CodeIndexer::new(
+                        os.clone(), index_name, String::new(), 100,
+                    );
+                    let now = chrono::Utc::now().timestamp_millis();
+                    for sym in &idx.symbols {
+                        indexer.add(crate::code_index::schema::SymbolDocument {
+                            file_path: sym.file_path.clone(),
+                            repo_owner: None,
+                            repo_name: idx.project_name.clone(),
+                            language: sym.language.clone(),
+                            symbol_name: sym.name.clone(),
+                            symbol_kind: sym.kind.clone(),
+                            signature: sym.signature.clone(),
+                            docstring: sym.docstring.clone(),
+                            start_line: sym.start_line as u32,
+                            end_line: sym.end_line as u32,
+                            content: sym.content.clone(),
+                            branch: idx.branch.clone(),
+                            source: "local".into(),
+                            indexed_at: now,
+                        }).await;
+                    }
+                    indexer.flush().await;
+                    info!(count = idx.symbols.len(), project = idx.project_name.as_str(), "Indexed client symbols");
+                }
+            }
             Some(client_message::Payload::End(_)) => {
                 session.end();
                 tx.send(Ok(ServerMessage {