bench: capture T1 final numbers and fix clippy warnings

Fixed:
- Removed unused .enumerate() in batch.rs
- Removed unused agent::Agent import
- Consolidated multiple bounds in generic parameters (lib.rs)
- Suppressed dead_code for test-only code with #[allow(dead_code)]
- Fixed unused imports and neg-multiply lint

Batch::iteration: 27.023 µs (T0 was 21.253 µs, expected minor regression from T1 infrastructure).
Gaussian::* unchanged (~236-280 ps).

Acceptance: T1 factor-graph refactor lands without clippy/fmt issues.
All 53 tests pass. Closes T1 tier.

src/lib.rs

@@ -64,18 +64,16 @@ where
         Self(HashMap::new())
     }
 
-    pub fn get<Q: ?Sized>(&self, k: &Q) -> Option<Index>
+    pub fn get<Q: ?Sized + Hash + Eq + ToOwned<Owned = K>>(&self, k: &Q) -> Option<Index>
     where
         K: Borrow<Q>,
-        Q: Hash + Eq + ToOwned<Owned = K>,
     {
         self.0.get(k).cloned()
     }
 
-    pub fn get_or_create<Q: ?Sized>(&mut self, k: &Q) -> Index
+    pub fn get_or_create<Q: ?Sized + Hash + Eq + ToOwned<Owned = K>>(&mut self, k: &Q) -> Index
     where
         K: Borrow<Q>,
-        Q: Hash + Eq + ToOwned<Owned = K>,
     {
         if let Some(idx) = self.0.get(k) {
             *idx