feat: search_tool migrate to bring you own tool of Responses API (#14274)

## Why

to support a new bring your own search tool in Responses
API(https://developers.openai.com/api/docs/guides/tools-tool-search#client-executed-tool-search)
we migrating our bm25 search tool to use official way to execute search
on client and communicate additional tools to the model.

## What
- replace the legacy `search_tool_bm25` flow with client-executed
`tool_search`
- add protocol, SSE, history, and normalization support for
`tool_search_call` and `tool_search_output`
- return namespaced Codex Apps search results and wire namespaced
follow-up tool calls back into MCP dispatch

codex-rs/rmcp-client/src/rmcp_client.rs

@@ -451,6 +451,7 @@ pub struct ToolWithConnectorId {
     pub tool: Tool,
     pub connector_id: Option<String>,
     pub connector_name: Option<String>,
+    pub connector_description: Option<String>,
 }
 
 pub struct ListToolsWithConnectorIdResult {
@@ -616,10 +617,13 @@ impl RmcpClient {
                 let connector_id = Self::meta_string(meta, "connector_id");
                 let connector_name = Self::meta_string(meta, "connector_name")
                     .or_else(|| Self::meta_string(meta, "connector_display_name"));
+                let connector_description = Self::meta_string(meta, "connector_description")
+                    .or_else(|| Self::meta_string(meta, "connectorDescription"));
                 Ok(ToolWithConnectorId {
                     tool,
                     connector_id,
                     connector_name,
+                    connector_description,
                 })
             })
             .collect::<Result<Vec<_>>>()?;