[codex] core: restore absolute turn context cwd (#28629)

## Why

#28152 jumped the gun on moving the rollout format to store URIs, and
would likely break compat with some features that don't go through the
same types as the core logic.

## What

Make `TurnContextItem.cwd` an `AbsolutePathBuf` again, remove test added
for `PathUri` serialization in rollouts. Also drops a bunch of error
paths that are no longer needed.

codex-rs/core/src/context_manager/history_tests.rs

@@ -21,9 +21,9 @@ use codex_protocol::protocol::AskForApproval;
 use codex_protocol::protocol::InterAgentCommunication;
 use codex_protocol::protocol::SandboxPolicy;
 use codex_protocol::protocol::TurnContextItem;
+use codex_utils_absolute_path::AbsolutePathBuf;
 use codex_utils_output_truncation::TruncationPolicy;
 use codex_utils_output_truncation::truncate_text;
-use codex_utils_path_uri::PathUri;
 use image::ImageBuffer;
 use image::ImageFormat;
 use image::Luma;
@@ -127,7 +127,7 @@ fn developer_msg_with_fragments(texts: &[&str]) -> ResponseItem {
 fn reference_context_item() -> TurnContextItem {
     TurnContextItem {
         turn_id: Some("reference-turn".to_string()),
-        cwd: PathUri::from_path(
+        cwd: AbsolutePathBuf::try_from(
             std::env::current_dir()
                 .expect("current directory")
                 .join("reference-cwd"),

codex-rs/core/src/context_manager/updates.rs

@@ -22,44 +22,40 @@ fn build_environment_update_item(
     previous: Option<&TurnContextItem>,
     next: &TurnContext,
     shell: &Shell,
-) -> std::io::Result<Option<ResponseItem>> {
+) -> Option<ResponseItem> {
     if !next.config.include_environment_context {
-        return Ok(None);
+        return None;
     }
 
-    let Some(prev) = previous else {
-        return Ok(None);
-    };
-    let prev_context = EnvironmentContext::from_turn_context_item(prev, shell.name().to_string())?;
+    let prev = previous?;
+    let prev_context = EnvironmentContext::from_turn_context_item(prev, shell.name().to_string());
     let next_context = EnvironmentContext::from_turn_context(next, shell);
     if prev_context.equals_except_shell(&next_context) {
-        return Ok(None);
+        return None;
     }
 
-    Ok(Some(ContextualUserFragment::into(
-        EnvironmentContext::diff_from_turn_context_item(prev, &next_context)?,
-    )))
+    Some(ContextualUserFragment::into(
+        EnvironmentContext::diff_from_turn_context_item(prev, &next_context),
+    ))
 }
 
 fn build_permissions_update_item(
     previous: Option<&TurnContextItem>,
     next: &TurnContext,
     exec_policy: &Policy,
-) -> std::io::Result<Option<String>> {
+) -> Option<String> {
     if !next.config.include_permissions_instructions {
-        return Ok(None);
+        return None;
     }
 
-    let Some(prev) = previous else {
-        return Ok(None);
-    };
-    if prev.permission_profile()? == next.permission_profile()
+    let prev = previous?;
+    if prev.permission_profile() == next.permission_profile()
         && prev.approval_policy == next.approval_policy.value()
     {
-        return Ok(None);
+        return None;
     }
 
-    Ok(Some(
+    Some(
         PermissionsInstructions::from_permission_profile(
             &next.permission_profile,
             next.approval_policy.value(),
@@ -71,7 +67,7 @@ fn build_permissions_update_item(
             next.features.enabled(Feature::RequestPermissionsTool),
         )
         .render(),
-    ))
+    )
 }
 
 fn build_collaboration_mode_update_item(
@@ -218,17 +214,17 @@ pub(crate) fn build_settings_update_items(
     shell: &Shell,
     exec_policy: &Policy,
     personality_feature_enabled: bool,
-) -> std::io::Result<Vec<ResponseItem>> {
+) -> Vec<ResponseItem> {
     // TODO(ccunningham): build_settings_update_items still does not cover every
     // model-visible item emitted by build_initial_context. Persist the remaining
     // inputs or add explicit replay events so fork/resume can diff everything
     // deterministically.
-    let contextual_user_message = build_environment_update_item(previous, next, shell)?;
+    let contextual_user_message = build_environment_update_item(previous, next, shell);
     let developer_update_sections = [
         // Keep model-switch instructions first so model-specific guidance is read before
         // any other context diffs on this turn.
         build_model_instructions_update_item(previous_turn_settings, next),
-        build_permissions_update_item(previous, next, exec_policy)?,
+        build_permissions_update_item(previous, next, exec_policy),
         build_collaboration_mode_update_item(previous, next),
         build_realtime_update_item(previous, previous_turn_settings, next),
         build_personality_update_item(previous, next, personality_feature_enabled),
@@ -244,5 +240,5 @@ pub(crate) fn build_settings_update_items(
     if let Some(contextual_user_message) = contextual_user_message {
         items.push(contextual_user_message);
     }
-    Ok(items)
+    items
 }