hive-c0re: extract read_from so the prune_unknown test exercises the real wiring

hive-c0re/src/agent_config/tool_groups.rs

@@ -41,7 +41,11 @@ pub fn tool_groups_path() -> PathBuf {
 /// honoured — but `read` itself never writes; unknown names stay on disk
 /// until the next `set_groups` rewrites the file.
 pub fn read() -> std::io::Result<BTreeMap<String, Vec<String>>> {
-    let mut map = super::read_map(&tool_groups_path())?;
+    read_from(&tool_groups_path())
+}
+
+fn read_from(path: &Path) -> std::io::Result<BTreeMap<String, Vec<String>>> {
+    let mut map = super::read_map(path)?;
     prune_unknown(&mut map);
     Ok(map)
 }
@@ -214,16 +218,15 @@ mod tests {
     }
 
     #[test]
-    fn read_drops_an_unknown_name_still_on_disk_without_rewriting_the_file() {
+    fn read_from_drops_an_unknown_name_still_on_disk_without_rewriting_the_file() {
         let dir = tempfile::tempdir().expect("tempdir");
         let path = dir.path().join(TOOL_GROUPS_FILE);
         std::fs::write(&path, r#"{"alice": ["messaging", "diagnostics"]}"#).expect("seed");
 
-        let map: BTreeMap<String, Vec<String>> = {
-            let mut m = crate::agent_config::read_map(&path).expect("read");
-            prune_unknown(&mut m);
-            m
-        };
+        // Exercises `read()`'s own wiring, not a hand-rolled equivalent —
+        // deleting the `prune_unknown` call inside `read_from` must fail
+        // this assertion.
+        let map = read_from(&path).expect("read_from");
         assert_eq!(map["alice"], vec!["messaging".to_owned()]);
 
         // `read()` itself never writes — the stale name is still on disk.