fix: serialize configure locator updates (#416)

Summary:
- Apply configure updates and long-lived locator reconfiguration under
the same configuration write lock.
- Keep refresh-state sync from interleaving with shared locator
reconfiguration.
- Add a regression test that blocks locator configuration and verifies
configuration readers cannot observe the new state early.

Validation:
- cargo test -p pet
test_configure_publishes_state_after_shared_locators_are_configured
- cargo test -p pet jsonrpc::tests::test_
- cargo fmt --all
- cargo clippy --all -- -D warnings

Fixes #385

Author: karthiknadig

crates/pet-virtualenvwrapper/src/environments.rs

@@ -190,7 +190,7 @@ mod tests {
 
     #[test]
     fn get_project_reads_existing_project_path_from_project_file() {
-        let project_root = create_test_dir("project-root");
+        let project_root = fs::canonicalize(create_test_dir("project-root")).unwrap();
         let prefix = create_test_dir("wrapped-env");
         let executable = create_virtualenv(&prefix);
         fs::write(