chore: enusre the logic that creates ConfigLayerStack has access to cwd (#8353)

`load_config_layers_state()` should load config from a
`.codex/config.toml` in any folder between the `cwd` for a thread and
the project root. Though in order to do that,
`load_config_layers_state()` needs to know what the `cwd` is, so this PR
does the work to thread the `cwd` through for existing callsites.

A notable exception is the `/config` endpoint in app server for which a
`cwd` is not guaranteed to be associated with the query, so the `cwd`
param is `Option<AbsolutePathBuf>` to account for this case.

The logic to make use of the `cwd` will be done in a follow-up PR.

codex-rs/tui2/src/lib.rs

@@ -23,6 +23,7 @@ use codex_core::find_conversation_path_by_id_str;
 use codex_core::get_platform_sandbox;
 use codex_core::protocol::AskForApproval;
 use codex_protocol::config_types::SandboxMode;
+use codex_utils_absolute_path::AbsolutePathBuf;
 use std::fs::OpenOptions;
 use std::path::PathBuf;
 use tracing::error;
@@ -153,15 +154,26 @@ pub async fn run_main(
         }
     };
 
+    let cwd = cli.cwd.clone();
+    let config_cwd = match cwd.as_deref() {
+        Some(path) => AbsolutePathBuf::from_absolute_path(path.canonicalize()?)?,
+        None => AbsolutePathBuf::current_dir()?,
+    };
+
     #[allow(clippy::print_stderr)]
-    let config_toml =
-        match load_config_as_toml_with_cli_overrides(&codex_home, cli_kv_overrides.clone()).await {
-            Ok(config_toml) => config_toml,
-            Err(err) => {
-                eprintln!("Error loading config.toml: {err}");
-                std::process::exit(1);
-            }
-        };
+    let config_toml = match load_config_as_toml_with_cli_overrides(
+        &codex_home,
+        &config_cwd,
+        cli_kv_overrides.clone(),
+    )
+    .await
+    {
+        Ok(config_toml) => config_toml,
+        Err(err) => {
+            eprintln!("Error loading config.toml: {err}");
+            std::process::exit(1);
+        }
+    };
 
     let model_provider_override = if cli.oss {
         let resolved = resolve_oss_provider(
@@ -199,8 +211,6 @@ pub async fn run_main(
         None // No model specified, will use the default.
     };
 
-    // 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 {