[codex] Add params-only Debug and SearchResults serde

Cargo.toml

@@ -65,6 +65,7 @@ all-features = false
 
 [dependencies]
 rayon = "1.10"
+serde = { version = "1.0", features = ["derive"], optional = true }
 
 [dev-dependencies]
 # Test/bench corpora are seeded with these; not needed by the library.
@@ -78,6 +79,7 @@ rand_chacha = "0.10"
 # target takes the scalar fallback. `experimental` exposes MultiBucketBitmap
 # (research scaffold), kept off the stable surface.
 experimental = []
+serde = ["dep:serde"]
 # `test-utils` exposes internal dispatch probes used by the crate's own integration
 # tests (e.g. the allocation-free guarantee check). Gated off the default surface
 # because these helpers are not part of the public API and carry no semver guarantee.

docs/msrv-and-features.md

@@ -19,7 +19,7 @@ any migration note.
 
 | Surface | Default features | Stable default-off features | Optional dependency features | Experimental/internal features |
 | --- | --- | --- | --- | --- |
-| `ordvec` | none | none | none | `experimental` exposes `MultiBucketBitmap`; `test-utils` is repo-test-only and has no public stability promise. |
+| `ordvec` | none | `serde` derives `Serialize`/`Deserialize` for `SearchResults` only | `serde` | `experimental` exposes `MultiBucketBitmap`; `test-utils` is repo-test-only and has no public stability promise. |
 | `ordvec-manifest` | none | none | `cli`, `sqlite`, `sqlite-bundled` | none |
 | `ordvec-python` | n/a | n/a | n/a | n/a |
 | `ordvec-manifest-python` | n/a | n/a | n/a | n/a |

src/bitmap.rs

@@ -56,6 +56,17 @@ pub struct Bitmap {
     bitmaps: Vec<u64>,
 }
 
+impl std::fmt::Debug for Bitmap {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("Bitmap")
+            .field("dim", &self.dim)
+            .field("n_top", &self.n_top)
+            .field("n_vectors", &self.n_vectors)
+            .field("bytes_per_vector", &self.bytes_per_vec())
+            .finish()
+    }
+}
+
 impl Bitmap {
     pub fn validate_params(dim: usize, n_top: usize) -> Result<(), OrdvecError> {
         if dim == 0 {

src/fastscan.rs

@@ -534,6 +534,15 @@ pub struct RankQuantFastscan {
     packed_fs: Vec<u8>,
 }
 
+impl std::fmt::Debug for RankQuantFastscan {
+    fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
+        f.debug_struct("RankQuantFastscan")
+            .field("dim", &self.dim)
+            .field("n_vectors", &self.n_vectors)
+            .finish()
+    }
+}
+
 impl RankQuantFastscan {
     /// Construct an empty FastScan b=2 index.
     ///