Stub reader-magnet welcome course, active: false pending Cate's story

Placeholder welcome-email copy in Cate's voice (Fantasy Michigan), wired
end-to-end but not enrollable until the real manuscript/cover/epub land.

courses/reader-magnet/day-1.md

@@ -0,0 +1,15 @@
+---
+subject: "About [STORY TITLE]..."
+---
+
+So — [STORY TITLE].
+
+[TODO: a line or two of behind-the-scenes color. What in Michigan inspired
+this one? What's the next book/story in this world?]
+
+I'll write again when there's real news — a new release, an event, or
+just another story worth sending. No spam, no noise.
+
+Thanks for reading,
+
+Cate