feat(ingestion): add wiki page merge logic

ingestion/internal/wiki/merge_test.go

@@ -0,0 +1,55 @@
+// ingestion/internal/wiki/merge_test.go
+package wiki
+
+import (
+	"strings"
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestMerge_BulletSectionsUnion(t *testing.T) {
+	a := Page{Path: "wiki/concepts/foo.md", Content: "---\ntitle: Foo\n---\n\n## Related Concepts\n\n- [[bar|Bar]]\n"}
+	b := Page{Path: "wiki/concepts/foo.md", Content: "---\ntitle: Foo\n---\n\n## Related Concepts\n\n- [[bar|Bar]]\n- [[baz|Baz]]\n"}
+
+	got := Merge(a, b)
+	assert.Contains(t, got.Content, "[[bar|Bar]]")
+	assert.Contains(t, got.Content, "[[baz|Baz]]")
+	assert.Equal(t, 1, strings.Count(got.Content, "[[bar|Bar]]"))
+}
+
+func TestMerge_AppendSections(t *testing.T) {
+	a := Page{Path: "wiki/concepts/foo.md", Content: "---\ntitle: Foo\n---\n\n## Evolving Notes\n\nFirst note.\n"}
+	b := Page{Path: "wiki/concepts/foo.md", Content: "---\ntitle: Foo\n---\n\n## Evolving Notes\n\nSecond note.\n"}
+
+	got := Merge(a, b)
+	assert.Contains(t, got.Content, "First note.")
+	assert.Contains(t, got.Content, "Second note.")
+}
+
+func TestMerge_KeepFirstForOtherSections(t *testing.T) {
+	a := Page{Path: "wiki/concepts/foo.md", Content: "---\ntitle: Foo\n---\n\n## Definition\n\nFirst definition.\n"}
+	b := Page{Path: "wiki/concepts/foo.md", Content: "---\ntitle: Foo\n---\n\n## Definition\n\nSecond definition.\n"}
+
+	got := Merge(a, b)
+	assert.Contains(t, got.Content, "First definition.")
+	assert.NotContains(t, got.Content, "Second definition.")
+}
+
+func TestMerge_NewSectionFromB(t *testing.T) {
+	a := Page{Path: "wiki/concepts/foo.md", Content: "---\ntitle: Foo\n---\n\n## Definition\n\nA thing.\n"}
+	b := Page{Path: "wiki/concepts/foo.md", Content: "---\ntitle: Foo\n---\n\n## Why It Matters\n\nBecause reasons.\n"}
+
+	got := Merge(a, b)
+	assert.Contains(t, got.Content, "A thing.")
+	assert.Contains(t, got.Content, "Because reasons.")
+}
+
+func TestMerge_KeepsFrontmatterFromA(t *testing.T) {
+	a := Page{Path: "p.md", Content: "---\ntitle: A\nlast_updated: 2026-01-01\n---\n\n## Definition\n\nA.\n"}
+	b := Page{Path: "p.md", Content: "---\ntitle: B\nlast_updated: 2026-06-01\n---\n\n## Definition\n\nB.\n"}
+
+	got := Merge(a, b)
+	assert.Contains(t, got.Content, "title: A")
+	assert.NotContains(t, got.Content, "title: B")
+}