Allow omitting MCP tool prefixes per server (#34991)

## What changed

- Accept a table form of `features.non_prefixed_mcp_tool_names` with an
  optional `server_names` list while preserving the existing boolean form.
- Omit the legacy `mcp__` namespace prefix only for tools from selected MCP
  servers. When no server list is provided, the enabled feature continues to
  omit the prefix for every server.
- Cover configuration resolution, tool normalization, and an MCP stdio
  round trip with selected servers.

GitOrigin-RevId: bdfb7ac54226de5051f06610e2c6b78b23912ef0

codex-rs/codex-mcp/src/tools.rs

@@ -109,10 +109,11 @@ pub(crate) fn filter_tools(tools: Vec<ToolInfo>, filter: &ToolFilter) -> Vec<Too
 /// every model-visible name is unique and <= 64 bytes.
 ///
 /// When `prefix_mcp_tool_names` is true, the historical `mcp__` namespace
-/// prefix is added without restoring the old trailing `__` namespace suffix.
+/// prefix is added except for tools from `non_prefixed_mcp_tool_servers`.
 pub(crate) fn normalize_tools_for_model_with_prefix<I>(
     tools: I,
     prefix_mcp_tool_names: bool,
+    non_prefixed_mcp_tool_servers: &[String],
 ) -> Vec<ToolInfo>
 where
     I: IntoIterator<Item = ToolInfo>,
@@ -137,7 +138,7 @@ where
 
         let callable_namespace = callable_namespace_with_prefix(
             &sanitize_responses_api_tool_name(&tool.callable_namespace),
-            prefix_mcp_tool_names,
+            prefix_mcp_tool_names && !non_prefixed_mcp_tool_servers.contains(&tool.server_name),
         );
 
         candidates.push(CallableToolCandidate {