Bind MCP calls to captured catalog revisions (#34588)

## Why

An MCP connection or tool catalog can change after a model step captures its
available tools. Calls from that step must not be rerouted to a replacement
client or run against a catalog revision the model did not see.

## What changed

- Add `McpBinding` to capture the ready clients, visible tools, resources, and
  server metadata for one sampling request.
- Prepare calls against the captured client and reject them if the tool catalog
  changes before call preparation and execution finish.
- Keep resource access and cache identity tied to the binding's exact connection
  set, and omit servers that do not have a ready client.
- Preserve each client's unfiltered tool catalog so bindings can apply the
  current filter consistently.

## Testing

Add coverage for connection replacement, stale catalog rejection, serialized
call preparation and refresh, ready-client capture, and binding-scoped resource
identity.

GitOrigin-RevId: a25da4d2c7f5ed06c41caa0c6d15c464c1698314

codex-rs/codex-mcp/src/lib.rs

@@ -1,3 +1,5 @@
+pub use binding::McpBinding;
+pub use binding::PreparedMcpCall;
 pub use connection_manager::McpConnectionManager;
 pub use connection_manager::tool_is_model_visible;
 pub use elicitation::ElicitationLifecycle;
@@ -82,6 +84,7 @@ pub use mcp::mcp_permission_prompt_is_auto_approved;
 pub use mcp::qualified_mcp_tool_name_prefix;
 
 pub(crate) mod auth_elicitation;
+mod binding;
 pub(crate) mod binding_clients;
 mod catalog;
 pub(crate) mod codex_apps;