revert(client-v2): restrict BFloat16 write to float per maintainer feedback

Reverts 0c70a36. Per maintainer review on #2934, BFloat16 is a
memory-optimization type for which only float is expected on write;
other input types are to be addressed per case rather than broadened up
front. Restores the direct (float) cast in SerializerUtils.serializePrimitiveData
and drops the broad-conversion / reject tests added in 0c70a36. The
exhaustive 65,536-pattern round-trip test is unchanged.

Author: polyglotAI-bot

client-v2/src/main/java/com/clickhouse/client/api/data_formats/internal/SerializerUtils.java

@@ -555,7 +555,7 @@ private static void serializePrimitiveData(OutputStream stream, Object value, Cl
                 BinaryStreamUtils.writeUnsignedInt256(stream, NumberConverter.toBigInteger(value));
                 break;
             case BFloat16:
-                BinaryStreamUtils.writeBFloat16(stream, NumberConverter.toFloat(value));
+                BinaryStreamUtils.writeBFloat16(stream, (float) value);
                 break;
             case Float32:
                 BinaryStreamUtils.writeFloat32(stream, NumberConverter.toFloat(value));

client-v2/src/test/java/com/clickhouse/client/api/data_formats/internal/SerializerUtilsPrimitiveSerializationTests.java

@@ -111,51 +111,6 @@ public void testSerializeFloatColumnRejectsUnsupportedValue() {
                 () -> serializeSingleValue("Float64", new Object()));
     }
 
-    @Test(dataProvider = "bFloat16ColumnValues")
-    public void testSerializeBFloat16ColumnFromVariousNumberTypes(Object value, float expected)
-            throws IOException {
-        RowBinaryWithNamesAndTypesFormatReader reader = serializeSingleValue("BFloat16", value);
-
-        reader.next();
-
-        Assert.assertEquals(reader.getFloat("value"), expected, 0.0f);
-    }
-
-    @DataProvider(name = "bFloat16ColumnValues")
-    private Object[][] bFloat16ColumnValues() {
-        // A non-Float value supplied for a BFloat16 column used to throw ClassCastException from the
-        // direct (float) cast; any Number now narrows through NumberConverter.toFloat (Number#floatValue()),
-        // matching the Float32/Float64 branches. Every value below is exactly representable in BFloat16
-        // (its float32 low 16 bits are zero), so the write-side truncation is lossless and the expected
-        // read-back is exact.
-        return new Object[][] {
-                // Same-type value keeps working unchanged (already passed before the fix).
-                {1.5f, 1.5f},
-
-                // A Double (and other Number subtypes) supplied for a BFloat16 column.
-                {1.5d, 1.5f},
-                {-2.5d, -2.5f},
-                {3, 3.0f},
-                {7L, 7.0f},
-                {(short) 5, 5.0f},
-                {(byte) 2, 2.0f},
-                {BigInteger.valueOf(9), 9.0f},
-                {new BigDecimal("1.5"), 1.5f},
-                {new CustomNumber("2.5"), 2.5f},
-
-                // String and Boolean are accepted too, matching the other numeric column branches.
-                {"1.5", 1.5f},
-                {true, 1.0f},
-                {false, 0.0f},
-        };
-    }
-
-    @Test
-    public void testSerializeBFloat16ColumnRejectsUnsupportedValue() {
-        Assert.assertThrows(IllegalArgumentException.class,
-                () -> serializeSingleValue("BFloat16", new Object()));
-    }
-
     @Test
     public void testSerializeBFloat16RoundTripAllValues() throws IOException {
         // Exhaustively round-trip every one of the 2^16 BFloat16 bit patterns. For pattern b the