Refactor to use new ACP crate (#35043)

This will prepare us for running the protocol over MCP

Release Notes:

- N/A

---------

Co-authored-by: Ben Brandt <benjamin.j.brandt@gmail.com>
Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>
Co-authored-by: Richard Feldman <oss@rtfeldman.com>

crates/agent_ui/src/agent_panel.rs

@@ -440,7 +440,7 @@ pub struct AgentPanel {
     local_timezone: UtcOffset,
     active_view: ActiveView,
     acp_message_history:
-        Rc<RefCell<crate::acp::MessageHistory<agentic_coding_protocol::SendUserMessageParams>>>,
+        Rc<RefCell<crate::acp::MessageHistory<Vec<agent_client_protocol::ContentBlock>>>>,
     previous_view: Option<ActiveView>,
     history_store: Entity<HistoryStore>,
     history: Entity<ThreadHistory>,