app-server: preserve target-native environment cwd (#28146)

## Why

app-server may run on a different OS from the selected exec-server
environment. Parsing that environment’s cwd with the Codex host’s path
rules prevents thread startup.

## What

Carry environment cwd values as `LegacyAppPathString` at the app-server
boundary and `PathUri` internally. Existing tool-call schemas and
relative-path behavior stay host-native; remaining local-only consumers
convert explicitly and leave follow-up TODOs.

The Wine integration test verifies app-server can start a thread and
complete an ordinary turn with a Windows environment cwd from Linux.

## Validation

- `bazel test //codex-rs/core/tests/remote_env_windows:smoke-test
--test_output=errors`
- focused app-server environment-selection and protocol schema tests
- scoped Clippy for `codex-core` and `codex-app-server-protocol`

codex-rs/app-server/src/request_processors/thread_processor.rs

@@ -4,7 +4,6 @@ use codex_app_server_protocol::SelectedCapabilityRoot;
 use codex_extension_api::ExtensionDataInit;
 use codex_protocol::models::BUILT_IN_PERMISSION_PROFILE_DANGER_FULL_ACCESS;
 use codex_protocol::models::BUILT_IN_PERMISSION_PROFILE_WORKSPACE;
-use codex_utils_path_uri::PathUri;
 
 const THREAD_LIST_DEFAULT_LIMIT: usize = 25;
 const THREAD_LIST_MAX_LIMIT: usize = 100;
@@ -906,7 +905,8 @@ impl ThreadRequestProcessor {
                 "`permissions` cannot be combined with `sandbox`",
             ));
         }
-        let environment_selections = self.parse_environment_selections(environments)?;
+        let environment_selections =
+            resolve_turn_environment_selections(self.thread_manager.as_ref(), environments)?;
         let runtime_workspace_roots = runtime_workspace_roots.map(resolve_runtime_workspace_roots);
         let mut typesafe_overrides = self.build_thread_config_overrides(
             model,
@@ -1311,27 +1311,6 @@ impl ThreadRequestProcessor {
         }
     }
 
-    fn parse_environment_selections(
-        &self,
-        environments: Option<Vec<TurnEnvironmentParams>>,
-    ) -> Result<Option<Vec<TurnEnvironmentSelection>>, JSONRPCErrorError> {
-        let environment_selections = environments.map(|environments| {
-            environments
-                .into_iter()
-                .map(|environment| TurnEnvironmentSelection {
-                    environment_id: environment.environment_id,
-                    cwd: PathUri::from_abs_path(&environment.cwd),
-                })
-                .collect::<Vec<_>>()
-        });
-        if let Some(environment_selections) = environment_selections.as_ref() {
-            self.thread_manager
-                .validate_environment_selections(environment_selections)
-                .map_err(environment_selection_error)?;
-        }
-        Ok(environment_selections)
-    }
-
     async fn thread_archive_inner(
         &self,
         params: ThreadArchiveParams,