Fix clippy lints in backfill and libraries tests

Keep `cargo clippy --tests` clean alongside the agentic-loop changes:
alias backfill's five-element setup() tuple as SetupFixture
(type_complexity) and build the single-library health map via
std::slice::from_ref instead of cloning (unnecessary clone-to-slice).
No behavior change.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

src/backfill.rs

@@ -529,16 +529,21 @@ mod tests {
         opentelemetry::Context::new()
     }
 
-    /// Build a tempdir-backed library + DAOs sharing a single in-memory
+    /// Everything `setup` hands back to a test: tempdir, library, shared
-    /// SQLite connection (so cross-table joins like
+    /// connection, and the two DAOs. Aliased to keep clippy's
-    /// `list_unscanned_candidates` see consistent state).
+    /// type-complexity lint satisfied.
-    fn setup() -> (
+    type SetupFixture = (
         TempDir,
         Library,
         Arc<Mutex<diesel::SqliteConnection>>,
         Arc<Mutex<Box<dyn ExifDao>>>,
         Arc<Mutex<Box<dyn FaceDao>>>,
-    ) {
+    );
+
+    /// Build a tempdir-backed library + DAOs sharing a single in-memory
+    /// SQLite connection (so cross-table joins like
+    /// `list_unscanned_candidates` see consistent state).
+    fn setup() -> SetupFixture {
         let tmp = TempDir::new().expect("tempdir");
         let mut conn = in_memory_db_connection();
         // Migration seeds library id=1 with a placeholder root; rewrite it

src/libraries.rs

@@ -1052,7 +1052,7 @@ mod tests {
             enabled: true,
             excluded_dirs: Vec::new(),
         };
-        let map = new_health_map(&[lib.clone()]);
+        let map = new_health_map(std::slice::from_ref(&lib));
 
         // First probe: empty dir, no prior data — Online.
         let s1 = refresh_health(&map, &lib, false);