fix: preserve adaptive IVF probe defaults (#4168)

Keep IVF probe fields unset by default so Lance supplies adaptive
behavior. Preserve `nprobes`, `minimum_nprobes`, and `maximum_nprobes`
independently through Rust, Python, namespace, and remote request
construction, with compatibility fields serialized only when explicitly
configured.

The final Rust namespace and LSM propagation update depends on the Lance
release containing lance-format/lance#9184.

python/src/query.rs

@@ -336,9 +336,8 @@ pub struct PyQueryRequest {
     pub use_lsm: Option<bool>,
     pub column: Option<String>,
     pub query_vector: Option<PyQueryVectors>,
+    pub nprobes: Option<usize>,
     pub minimum_nprobes: Option<usize>,
-    // None means user did not set it and default should be used (currently 20)
-    // Some(0) means user set it to None and there is no limit
     pub maximum_nprobes: Option<usize>,
     pub lower_bound: Option<f32>,
     pub upper_bound: Option<f32>,
@@ -369,6 +368,7 @@ impl From<AnyQuery> for PyQueryRequest {
                 use_lsm: query_request.use_lsm,
                 column: None,
                 query_vector: None,
+                nprobes: None,
                 minimum_nprobes: None,
                 maximum_nprobes: None,
                 lower_bound: None,
@@ -396,11 +396,9 @@ impl From<AnyQuery> for PyQueryRequest {
                 use_lsm: vector_query.base.use_lsm,
                 column: vector_query.column,
                 query_vector: Some(PyQueryVectors(vector_query.query_vector)),
-                minimum_nprobes: Some(vector_query.minimum_nprobes),
-                maximum_nprobes: match vector_query.maximum_nprobes {
-                    None => Some(0),
-                    Some(value) => Some(value),
-                },
+                nprobes: vector_query.nprobes,
+                minimum_nprobes: vector_query.minimum_nprobes,
+                maximum_nprobes: vector_query.maximum_nprobes,
                 lower_bound: vector_query.lower_bound,
                 upper_bound: vector_query.upper_bound,
                 ef: vector_query.ef,