[codex] migrate ExecutorFileSystem paths to PathUri (#27424)

## Why

We're moving exec-server to use PathUri for its internal path
representations.

## What

Move `ExecutorFileSystem` APIs to use `PathUri` instead of
`AbsolutePathBuf`. Future changes will convert higher-level parts of
exec-server.

codex-rs/exec-server/src/environment.rs

@@ -882,6 +882,7 @@ mod tests {
             std::env::current_exe().expect("current exe").as_path(),
         )
         .expect("absolute current exe");
+        let path = codex_utils_path_uri::PathUri::from_abs_path(&path).expect("path URI");
         let sandbox = crate::FileSystemSandboxContext::from_permission_profile(
             codex_protocol::models::PermissionProfile::from_runtime_permissions(
                 &codex_protocol::permissions::FileSystemSandboxPolicy::restricted(Vec::new()),