feat: add visible pod discovery tools

crates/session-store/src/fs_store.rs

@@ -123,6 +123,35 @@ impl PodMetadataStore for FsStore {
         Ok(Some(serde_json::from_str(&content)?))
     }
 
+    fn list_names(&self) -> Result<Vec<String>, StoreError> {
+        let dir = self.pods_dir();
+        let mut names = Vec::new();
+        if !dir.exists() {
+            return Ok(names);
+        }
+        for entry in fs::read_dir(dir)? {
+            let entry = entry?;
+            if !entry.file_type()?.is_dir() {
+                continue;
+            }
+            if !entry.path().join("metadata.json").exists() {
+                continue;
+            }
+            let Some(name) = entry.file_name().to_str().map(ToOwned::to_owned) else {
+                continue;
+            };
+            if validate_pod_name(&name).is_ok() {
+                names.push(name);
+            }
+        }
+        names.sort();
+        Ok(names)
+    }
+
+    fn root_dir(&self) -> Option<PathBuf> {
+        Some(self.root.clone())
+    }
+
     fn delete_by_name(&self, pod_name: &str) -> Result<(), StoreError> {
         let path = self.pod_metadata_path(pod_name)?;
         match fs::remove_file(&path) {

crates/session-store/src/pod_metadata.rs

@@ -92,6 +92,16 @@ pub trait PodMetadataStore: Send + Sync {
     /// Read metadata by Pod name. Returns `None` when no metadata exists.
     fn read_by_name(&self, pod_name: &str) -> Result<Option<PodMetadata>, StoreError>;
 
+    /// List persisted Pod metadata keys. Implementations return names only;
+    /// callers can then read each item independently so a corrupt metadata
+    /// file does not make the whole discovery result fail.
+    fn list_names(&self) -> Result<Vec<String>, StoreError>;
+
+    /// Return the metadata root directory when this backend is path-backed.
+    fn root_dir(&self) -> Option<PathBuf> {
+        None
+    }
+
     /// Delete metadata by Pod name. Missing metadata is a successful no-op.
     fn delete_by_name(&self, pod_name: &str) -> Result<(), StoreError>;
 }

crates/session-store/tests/fs_store_test.rs

@@ -250,6 +250,7 @@ fn pod_metadata_minimal_crud() {
 
     let pending = PodMetadata::new(pod_name, Some(PodActiveSegmentRef::pending_segment(sid)));
     store.write(&pending).unwrap();
+    assert_eq!(store.list_names().unwrap(), vec![pod_name.to_string()]);
     assert_eq!(store.read_by_name(pod_name).unwrap(), Some(pending.clone()));
     assert!(
         dir.path()