fix: make slug rename and content update atomic via RenameAndUpsertPost

Previously RenamePost + UpsertPost were two separate DB calls; a failure
between them left the post at the new slug with stale content. The new
RenameAndUpsertPost method does both in a single transaction.

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

1 files changed, 46 insertions, 0 deletions

diff --git a/internal/db/posts_test.go b/internal/db/posts_test.go
index 26664ce..1c3eb33 100644
--- a/internal/db/posts_test.go
+++ b/internal/db/posts_test.go
@@ -124,6 +124,52 @@ func TestRenamePost(t *testing.T) {
 	}
 }
 
+func TestRenameAndUpsertPost(t *testing.T) {
+	m := openTestDB(t)
+
+	if err := m.UpsertPost(PostRecord{Slug: "old", Title: "Old Title", Date: "2026-01-01", Blocks: "[]", UpdatedAt: 1}); err != nil {
+		t.Fatalf("UpsertPost: %v", err)
+	}
+
+	updated := PostRecord{
+		Slug:      "new",
+		Title:     "New Title",
+		Date:      "2026-04-04",
+		Tags:      []string{"go"},
+		Blocks:    "[]",
+		UpdatedAt: 2,
+	}
+	if err := m.RenameAndUpsertPost("old", updated); err != nil {
+		t.Fatalf("RenameAndUpsertPost: %v", err)
+	}
+
+	// New slug has updated content
+	got, err := m.GetPost("new")
+	if err != nil {
+		t.Fatalf("GetPost new: %v", err)
+	}
+	if got.Title != "New Title" {
+		t.Errorf("title: got %q, want %q", got.Title, "New Title")
+	}
+	if got.Date != "2026-04-04" {
+		t.Errorf("date: got %q, want %q", got.Date, "2026-04-04")
+	}
+
+	// Old slug is gone
+	if _, err := m.GetPost("old"); err == nil {
+		t.Error("expected old slug to be deleted")
+	}
+
+	// Redirect created
+	toSlug, err := m.GetRedirect("old")
+	if err != nil {
+		t.Fatalf("GetRedirect: %v", err)
+	}
+	if toSlug != "new" {
+		t.Errorf("redirect: got %q, want %q", toSlug, "new")
+	}
+}
+
 func TestRenamePost_CollapsesChain(t *testing.T) {
 	m := openTestDB(t)