feat: add --add-dir flag for extra writable roots (#5335)

Add a `--add-dir` CLI flag so sessions can use extra writable roots in
addition to the ones specified in the config file. These are ephemerally
added during the session only.

Fixes #3303
Fixes #2797

codex-rs/tui/src/lib.rs

@@ -161,6 +161,7 @@ pub async fn run_main(
 
     // canonicalize the cwd
     let cwd = cli.cwd.clone().map(|p| p.canonicalize().unwrap_or(p));
+    let additional_dirs = cli.add_dir.clone();
 
     let overrides = ConfigOverrides {
         model,
@@ -177,6 +178,7 @@ pub async fn run_main(
         include_view_image_tool: None,
         show_raw_agent_reasoning: cli.oss.then_some(true),
         tools_web_search_request: cli.web_search.then_some(true),
+        additional_writable_roots: additional_dirs,
     };
     let raw_overrides = cli.config_overrides.raw_overrides.clone();
     let overrides_cli = codex_common::CliConfigOverrides { raw_overrides };