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:


https://github.com/openai/codex/blob/bcd64c7e7231d6316a2377d1525a0fa74f21b783/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/core/tests/suite/cli_stream.rs

@@ -75,9 +75,17 @@ async fn chat_mode_stream_cli() {
     server.verify().await;
 
     // Verify a new session rollout was created and is discoverable via list_conversations
-    let page = RolloutRecorder::list_conversations(home.path(), 10, None, &[])
-        .await
-        .expect("list conversations");
+    let provider_filter = vec!["mock".to_string()];
+    let page = RolloutRecorder::list_conversations(
+        home.path(),
+        10,
+        None,
+        &[],
+        Some(provider_filter.as_slice()),
+        "mock",
+    )
+    .await
+    .expect("list conversations");
     assert!(
         !page.items.is_empty(),
         "expected at least one session to be listed"

codex-rs/core/tests/suite/client.rs

@@ -154,7 +154,8 @@ async fn resume_includes_initial_messages_and_sends_prior_items() {
                 "instructions": "be nice",
                 "cwd": ".",
                 "originator": "test_originator",
-                "cli_version": "test_version"
+                "cli_version": "test_version",
+                "model_provider": "test-provider"
             }
         })
     )

codex-rs/core/tests/suite/review.rs

@@ -368,7 +368,8 @@ async fn review_input_isolated_from_parent_history() {
                 "instructions": null,
                 "cwd": ".",
                 "originator": "test_originator",
-                "cli_version": "test_version"
+                "cli_version": "test_version",
+                "model_provider": "test-provider"
             }
         });
         f.write_all(format!("{meta_line}\n").as_bytes())

codex-rs/core/tests/suite/rollout_list_find.rs

@@ -28,7 +28,8 @@ fn write_minimal_rollout_with_id(codex_home: &Path, id: Uuid) -> PathBuf {
                 "instructions": null,
                 "cwd": ".",
                 "originator": "test",
-                "cli_version": "test"
+                "cli_version": "test",
+                "model_provider": "test-provider"
             }
         })
     )