[app-server] feat: v2 Thread APIs (#6214)

Implements:
```
thread/list
thread/start
thread/resume
thread/archive
```

along with their integration tests. These are relatively light wrappers
around the existing core logic, and changes to core logic are minimal.

However, an improvement made for developer ergonomics:
- `thread/start` and `thread/resume` automatically attaches a
conversation listener internally, so clients don't have to make a
separate `AddConversationListener` call like they do today.

For consistency, also updated `model/list` and `feedback/upload` (naming
conventions, list API params).

codex-rs/app-server/tests/common/lib.rs

@@ -2,6 +2,7 @@ mod auth_fixtures;
 mod mcp_process;
 mod mock_model_server;
 mod responses;
+mod rollout;
 
 pub use auth_fixtures::ChatGptAuthFixture;
 pub use auth_fixtures::ChatGptIdTokenClaims;
@@ -10,9 +11,11 @@ pub use auth_fixtures::write_chatgpt_auth;
 use codex_app_server_protocol::JSONRPCResponse;
 pub use mcp_process::McpProcess;
 pub use mock_model_server::create_mock_chat_completions_server;
+pub use mock_model_server::create_mock_chat_completions_server_unchecked;
 pub use responses::create_apply_patch_sse_response;
 pub use responses::create_final_assistant_message_sse_response;
 pub use responses::create_shell_sse_response;
+pub use rollout::create_fake_rollout;
 use serde::de::DeserializeOwned;
 
 pub fn to_response<T: DeserializeOwned>(response: JSONRPCResponse) -> anyhow::Result<T> {