feat(scan): add withColumns/withLimit/withFilter fluent methods to ScanOptions

Allows chaining: ScanOptions.columns("price").withLimit(10).withFilter(...)
without touching the 3-arg record constructor. All methods return new
instances; original is unchanged.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: dfa1

reader/src/main/java/io/github/dfa1/vortex/scan/ScanOptions.java

@@ -25,6 +25,18 @@ public static ScanOptions limit(long limit) {
 		return new ScanOptions(List.of(), null, limit);
 	}
 
+	public ScanOptions withColumns(String... names) {
+		return new ScanOptions(List.of(names), rowFilter, limit);
+	}
+
+	public ScanOptions withLimit(long limit) {
+		return new ScanOptions(columns, rowFilter, limit);
+	}
+
+	public ScanOptions withFilter(RowFilter filter) {
+		return new ScanOptions(columns, filter, limit);
+	}
+
 	public boolean hasProjection() {
 		return !columns.isEmpty();
 	}

reader/src/test/java/io/github/dfa1/vortex/scan/ScanOptionsTest.java

@@ -0,0 +1,71 @@
+package io.github.dfa1.vortex.scan;
+
+import org.junit.jupiter.api.Test;
+
+import static org.assertj.core.api.Assertions.assertThat;
+
+class ScanOptionsTest {
+
+	@Test
+	void withLimit_setsLimit() {
+		// Given / When
+		ScanOptions sut = ScanOptions.all().withLimit(10);
+
+		// Then
+		assertThat(sut.limit()).isEqualTo(10);
+		assertThat(sut.hasLimit()).isTrue();
+		assertThat(sut.columns()).isEmpty();
+		assertThat(sut.rowFilter()).isNull();
+	}
+
+	@Test
+	void withColumns_setsProjection() {
+		// Given / When
+		ScanOptions sut = ScanOptions.all().withColumns("price", "qty");
+
+		// Then
+		assertThat(sut.columns()).containsExactly("price", "qty");
+		assertThat(sut.hasProjection()).isTrue();
+		assertThat(sut.limit()).isEqualTo(ScanOptions.NO_LIMIT);
+	}
+
+	@Test
+	void withFilter_setsFilter() {
+		// Given
+		RowFilter filter = new RowFilter.Gte("price", 100);
+
+		// When
+		ScanOptions sut = ScanOptions.all().withFilter(filter);
+
+		// Then
+		assertThat(sut.rowFilter()).isEqualTo(filter);
+		assertThat(sut.hasFilter()).isTrue();
+	}
+
+	@Test
+	void fluent_chainingPreservesAllFields() {
+		// Given / When
+		ScanOptions sut = ScanOptions.all()
+				.withColumns("price", "qty")
+				.withLimit(10)
+				.withFilter(new RowFilter.Gte("price", 50));
+
+		// Then
+		assertThat(sut.columns()).containsExactly("price", "qty");
+		assertThat(sut.limit()).isEqualTo(10);
+		assertThat(sut.hasFilter()).isTrue();
+	}
+
+	@Test
+	void withMethods_doNotMutateOriginal() {
+		// Given
+		ScanOptions original = ScanOptions.all();
+
+		// When
+		original.withLimit(5).withColumns("x");
+
+		// Then
+		assertThat(original.limit()).isEqualTo(ScanOptions.NO_LIMIT);
+		assertThat(original.columns()).isEmpty();
+	}
+}