fix(scanner): fence same-cycle caches with full activity coverage

Keep structural baseline identity separate from the full activity coverage
required by bucket admission and set publication. Require complete set
coverage proofs while retaining revision CAS and epoch regression checks.

Co-Authored-By: heihutu <heihutu@gmail.com>
Co-Authored-By: zhi22915 <qiuzgang@gmail.com>

crates/scanner/src/data_usage_define/tests.rs

@@ -29,6 +29,31 @@ use tokio::sync::Mutex;
 
 const TEST_PLAN_DIGEST: DataUsageScanPlanDigest = DataUsageScanPlanDigest([3; 32]);
 
+#[test]
+fn scoped_scan_coverage_metadata_preserves_map_compatibility() {
+    #[derive(serde::Deserialize)]
+    struct LegacyInfo {
+        name: String,
+        next_cycle: u64,
+    }
+    let mut info = DataUsageCacheInfo {
+        name: DATA_USAGE_ROOT.to_string(),
+        next_cycle: 7,
+        ..Default::default()
+    };
+    let old = serde_json::to_value(&info).expect("legacy metadata should encode");
+    assert!(old.get("scan_coverage_digest").is_none());
+    let old: DataUsageCacheInfo = serde_json::from_value(old).expect("missing coverage must remain readable");
+    assert!(old.scan_coverage_digest.is_none());
+    info.scan_coverage_digest = Some(TEST_PLAN_DIGEST);
+    let encoded = rmp_serde::to_vec(&info).expect("coverage metadata should remain map encoded");
+    let legacy: LegacyInfo = rmp_serde::from_slice(&encoded).expect("old map readers should ignore additive proof fields");
+    assert_eq!(legacy.name, DATA_USAGE_ROOT);
+    assert_eq!(legacy.next_cycle, 7);
+    let decoded: DataUsageCacheInfo = rmp_serde::from_slice(&encoded).expect("new reader should restore the coverage proof");
+    assert_eq!(decoded.scan_coverage_digest, Some(TEST_PLAN_DIGEST));
+}
+
 #[derive(Debug, PartialEq, Eq)]
 struct CachePutRecord {
     object: String,