Fix check_doc_in_cbs to query tombstones via XATTRs

The previous implementation used META().deleted which does not exist
in Couchbase N1QL. Tombstones cannot be queried directly via standard
N1QL queries.

With enable_shared_bucket_access: true, Sync Gateway stores metadata
in extended attributes (XATTRs). The _sync xattr contains the deleted
status and other sync metadata.

Changes:
- Query META().xattrs._sync.deleted instead of non-existent META().deleted
- Use USE KEYS syntax for direct document lookup
- Parse and display tombstone status clearly (TOMBSTONE vs LIVE document)
- Improve output messages to distinguish between purged vs existing docs

This fix enables the tests to properly detect tombstones in CBS and
verify whether they persist or get purged after compaction.

References:
- Sync Gateway docs on shared bucket access and tombstones
- Couchbase N1QL docs on XATTRs querying

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <[email protected]>

Author: pimpin

examples/utils/cbs_admin.rs

@@ -42,9 +42,11 @@ pub fn compact_cbs_bucket() {
 
 pub fn check_doc_in_cbs(doc_id: &str) {
     // Use port 8093 for Query service (not 8091 which is admin/REST API)
+    // Query XATTRs to see tombstones in shared bucket access mode
+    // The _sync xattr contains Sync Gateway metadata including deleted status
     let url = "http://localhost:8093/query/service";
     let query = format!(
-        "SELECT META().id, META().deleted FROM `{CBS_BUCKET}` WHERE META().id = '{doc_id}'"
+        "SELECT META().id, META().xattrs._sync.deleted as deleted FROM `{CBS_BUCKET}` USE KEYS ['{doc_id}']"
     );
     let body = serde_json::json!({"statement": query});
 
@@ -63,12 +65,25 @@ pub fn check_doc_in_cbs(doc_id: &str) {
                     if let Some(results) = json["results"].as_array() {
                         if results.is_empty() {
                             println!(
-                                "CBS check for {doc_id}: ✓ Document not found (successfully purged)"
+                                "CBS check for {doc_id}: ✓ Document not found (completely purged)"
                             );
                         } else {
                             println!("CBS check for {doc_id}: Found {} result(s)", results.len());
                             for result in results {
-                                println!("  - {}", serde_json::to_string_pretty(result).unwrap());
+                                let is_deleted = result["deleted"].as_bool().unwrap_or(false);
+                                if is_deleted {
+                                    println!("  - Document exists as TOMBSTONE (deleted: true)");
+                                    println!(
+                                        "    {}",
+                                        serde_json::to_string_pretty(result).unwrap()
+                                    );
+                                } else {
+                                    println!("  - Document exists as LIVE document");
+                                    println!(
+                                        "    {}",
+                                        serde_json::to_string_pretty(result).unwrap()
+                                    );
+                                }
                             }
                         }
                     } else {