feat: annotate conversations with model_provider for filtering (#5658)

Because conversations that use the Responses API can have encrypted
reasoning messages, trying to resume a conversation with a different
provider could lead to confusing "failed to decrypt" errors. (This is
reproducible by starting a conversation using ChatGPT login and resuming
it as a conversation that uses OpenAI models via Azure.)

This changes `ListConversationsParams` to take a `model_providers:
Option<Vec<String>>` and adds `model_provider` on each
`ConversationSummary` it returns so these cases can be disambiguated.

Note this ended up making changes to
`codex-rs/core/src/rollout/tests.rs` because it had a number of cases
where it expected `Some` for the value of `next_cursor`, but the list of
rollouts was complete, so according to this docstring:


bcd64c7e72/codex-rs/app-server-protocol/src/protocol.rs (L334-L337)

If there are no more items to return, then `next_cursor` should be
`None`. This PR updates that logic.






---
[//]: # (BEGIN SAPLING FOOTER)
Stack created with [Sapling](https://sapling-scm.com). Best reviewed
with [ReviewStack](https://reviewstack.dev/openai/codex/pull/5658).
* #5803
* #5793
* __->__ #5658

codex-rs/exec/src/lib.rs

@@ -389,8 +389,16 @@ async fn resolve_resume_path(
     args: &crate::cli::ResumeArgs,
 ) -> anyhow::Result<Option<PathBuf>> {
     if args.last {
-        match codex_core::RolloutRecorder::list_conversations(&config.codex_home, 1, None, &[])
-            .await
+        let default_provider_filter = vec![config.model_provider_id.clone()];
+        match codex_core::RolloutRecorder::list_conversations(
+            &config.codex_home,
+            1,
+            None,
+            &[],
+            Some(default_provider_filter.as_slice()),
+            &config.model_provider_id,
+        )
+        .await
         {
             Ok(page) => Ok(page.items.first().map(|it| it.path.clone())),
             Err(e) => {