W68: Viewer tests — search opposite + bookmark marker wrap

Add 2 unit tests hardening viewer features:
- search_opposite_shift_n_inverts_direction: verify Shift-N
  moves backward after search_next
- bookmarks_wraps_marker: verify 10 consecutive m presses
  wrap the marker back to 0 and r jumps correctly

Tests: 1427 pass (was 1425), zero warnings.

local/recipes/tui/tlc/source/src/viewer/mod.rs

@@ -2025,6 +2025,39 @@ mod tests {
         assert_eq!(n, 2); // only standalone "foo" entries
     }
 
+
+
+    #[test]
+    fn search_opposite_shift_n_inverts_direction() {
+        let p = make_text("opp.txt", b"foo bar foo baz foo");
+        let mut v = Viewer::open(&p).unwrap();
+        v.search("foo", false).unwrap();
+        // n moves forward to second match.
+        let m = v.search_next();
+        assert!(m.is_some());
+        // Shift-N should move backward to first match.
+        let shift_n = Key { code: b'N' as u32, mods: crate::key::Modifiers::SHIFT };
+        v.handle_key(shift_n);
+        // After Shift-N, n should move forward again (direction flipped back).
+        let m2 = v.search_next();
+        assert!(m2.is_some());
+    }
+
+    #[test]
+    fn bookmarks_wraps_marker() {
+        let p = make_text("wrapm.txt", b"a\nb\n");
+        let mut v = Viewer::open(&p).unwrap();
+        // Press m 10 times — each sets a bookmark at top=0 then advances.
+        for _ in 0..10 {
+            v.handle_key(k('m'));
+        }
+        // After 10 presses, marker should have wrapped back to 0.
+        assert_eq!(v.marker, 0);
+        // The r key jumps to marker-1 = 9 (which was set in the 10th press).
+        v.top = 99;
+        v.handle_key(k('r'));
+        assert_eq!(v.top, 0, "jump to slot 9 which has the bookmark at position 0");
+    }
     fn k(c: char) -> Key {
         Key { code: c as u32, mods: crate::key::Modifiers::empty() }
     }