generate an internal json schema for RolloutLine (#14434)

### Why
i'm working on something that parses and analyzes codex rollout logs,
and i'd like to have a schema for generating a parser/validator.

`codex app-server generate-internal-json-schema` writes an
`RolloutLine.json` file

while doing this, i noticed we have a writer <> reader mismatch issue on
`FunctionCallOutputPayload` and reasoning item ID -- added some schemars
annotations to fix those

### Test

```
$ just codex app-server generate-internal-json-schema --out ./foo
```

generates an `RolloutLine.json` file, which i validated against jsonl
files on disk

`just codex app-server --help` doesn't expose the
`generate-internal-json-schema` option by default, but you can do `just
codex app-server generate-internal-json-schema --help` if you know the
command

everything else still works

---------

Co-authored-by: Codex <noreply@openai.com>

codex-rs/cli/src/main.rs

@@ -351,12 +351,17 @@ struct AppServerCommand {
 }
 
 #[derive(Debug, clap::Subcommand)]
+#[allow(clippy::enum_variant_names)]
 enum AppServerSubcommand {
     /// [experimental] Generate TypeScript bindings for the app server protocol.
     GenerateTs(GenerateTsCommand),
 
     /// [experimental] Generate JSON Schema for the app server protocol.
     GenerateJsonSchema(GenerateJsonSchemaCommand),
+
+    /// [internal] Generate internal JSON Schema artifacts for Codex tooling.
+    #[clap(hide = true)]
+    GenerateInternalJsonSchema(GenerateInternalJsonSchemaCommand),
 }
 
 #[derive(Debug, Args)]
@@ -385,6 +390,13 @@ struct GenerateJsonSchemaCommand {
     experimental: bool,
 }
 
+#[derive(Debug, Args)]
+struct GenerateInternalJsonSchemaCommand {
+    /// Output directory where internal JSON Schema artifacts will be written
+    #[arg(short = 'o', long = "out", value_name = "DIR")]
+    out_dir: PathBuf,
+}
+
 #[derive(Debug, Parser)]
 struct StdioToUdsCommand {
     /// Path to the Unix domain socket to connect to.
@@ -665,6 +677,9 @@ async fn cli_main(arg0_paths: Arg0DispatchPaths) -> anyhow::Result<()> {
                     gen_cli.experimental,
                 )?;
             }
+            Some(AppServerSubcommand::GenerateInternalJsonSchema(gen_cli)) => {
+                codex_app_server_protocol::generate_internal_json_schema(&gen_cli.out_dir)?;
+            }
         },
         #[cfg(target_os = "macos")]
         Some(Subcommand::App(app_cli)) => {