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/exec/src/lib.rs

@@ -37,6 +37,7 @@ use codex_core::protocol::SessionSource;
 use codex_protocol::approvals::ElicitationAction;
 use codex_protocol::config_types::SandboxMode;
 use codex_protocol::user_input::UserInput;
+use codex_utils_absolute_path::AbsolutePathBuf;
 use event_processor_with_human_output::EventProcessorWithHumanOutput;
 use event_processor_with_jsonl_output::EventProcessorWithJsonOutput;
 use serde_json::Value;
@@ -132,6 +133,12 @@ pub async fn run_main(cli: Cli, codex_linux_sandbox_exe: Option<PathBuf>) -> any
         }
     };
 
+    let resolved_cwd = cwd.clone();
+    let config_cwd = match resolved_cwd.as_deref() {
+        Some(path) => AbsolutePathBuf::from_absolute_path(path.canonicalize()?)?,
+        None => AbsolutePathBuf::current_dir()?,
+    };
+
     // we load config.toml here to determine project state.
     #[allow(clippy::print_stderr)]
     let config_toml = {
@@ -143,7 +150,13 @@ pub async fn run_main(cli: Cli, codex_linux_sandbox_exe: Option<PathBuf>) -> any
             }
         };
 
-        match load_config_as_toml_with_cli_overrides(&codex_home, cli_kv_overrides.clone()).await {
+        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}");
@@ -190,7 +203,7 @@ pub async fn run_main(cli: Cli, codex_linux_sandbox_exe: Option<PathBuf>) -> any
         // Default to never ask for approvals in headless mode. Feature flags can override.
         approval_policy: Some(AskForApproval::Never),
         sandbox_mode,
-        cwd: cwd.map(|p| p.canonicalize().unwrap_or(p)),
+        cwd: resolved_cwd,
         model_provider: model_provider.clone(),
         codex_linux_sandbox_exe,
         base_instructions: None,