feat(acp-nats): add integration test suite for Bridge, handlers, and workflows

Add tests/ module with agent_handlers, builders, prefix, and workflows
integration tests covering session lifecycle, cancellation, and ext methods.

Signed-off-by: Yordis Prieto <yordis.prieto@gmail.com>

Author: yordis

rsworkspace/crates/acp-nats/src/lib.rs

@@ -12,6 +12,8 @@ pub mod prompt_slot_counter;
 pub mod session_id;
 pub mod subject_token_violation;
 pub(crate) mod telemetry;
+#[cfg(test)]
+mod tests;
 
 pub use acp_prefix::{AcpPrefix, AcpPrefixError};
 pub use agent::Bridge;