feat: add ZDR support to Rust implementation (#642)

This adds support for the `--disable-response-storage` flag across our
multiple Rust CLIs to support customers who have opted into Zero-Data
Retention (ZDR). The analogous changes to the TypeScript CLI were:

* https://github.com/openai/codex/pull/481
* https://github.com/openai/codex/pull/543

For a client using ZDR, `previous_response_id` will never be available,
so the `input` field of an API request must include the full transcript
of the conversation thus far. As such, this PR changes the type of
`Prompt.input` from `Vec<ResponseInputItem>` to `Vec<ResponseItem>`.

Practically speaking, `ResponseItem` was effectively a "superset" of
`ResponseInputItem` already. The main difference for us is that
`ResponseItem` includes the `FunctionCall` variant that we have to
include as part of the conversation history in the ZDR case.

Another key change in this PR is modifying `try_run_turn()` so that it
returns the `Vec<ResponseItem>` for the turn in addition to the
`Vec<ResponseInputItem>` produced by `try_run_turn()`. This is because
the caller of `run_turn()` needs to record the `Vec<ResponseItem>` when
ZDR is enabled.

To that end, this PR introduces `ZdrTranscript` (and adds
`zdr_transcript: Option<ZdrTranscript>` to `struct State` in `codex.rs`)
to take responsibility for maintaining the conversation transcript in
the ZDR case.

codex-rs/exec/src/cli.rs

@@ -16,6 +16,10 @@ pub struct Cli {
     #[arg(long = "skip-git-repo-check", default_value_t = false)]
     pub skip_git_repo_check: bool,
 
+    /// Disable server‑side response storage (sends the full conversation context with every request)
+    #[arg(long = "disable-response-storage", default_value_t = false)]
+    pub disable_response_storage: bool,
+
     /// Initial instructions for the agent.
     pub prompt: Option<String>,
 }

codex-rs/exec/src/lib.rs

@@ -31,9 +31,10 @@ pub async fn run_main(cli: Cli) -> anyhow::Result<()> {
         .try_init();
 
     let Cli {
-        skip_git_repo_check,
-        model,
         images,
+        model,
+        skip_git_repo_check,
+        disable_response_storage,
         prompt,
         ..
     } = cli;
@@ -50,8 +51,13 @@ pub async fn run_main(cli: Cli) -> anyhow::Result<()> {
     // likely come from a new --execution-policy arg.
     let approval_policy = AskForApproval::Never;
     let sandbox_policy = SandboxPolicy::NetworkAndFileWriteRestricted;
-    let (codex_wrapper, event, ctrl_c) =
-        codex_wrapper::init_codex(approval_policy, sandbox_policy, model).await?;
+    let (codex_wrapper, event, ctrl_c) = codex_wrapper::init_codex(
+        approval_policy,
+        sandbox_policy,
+        disable_response_storage,
+        model,
+    )
+    .await?;
     let codex = Arc::new(codex_wrapper);
     info!("Codex initialized with event: {event:?}");