Add 26.3 descriptive book binding and travel

docs/MINECRAFT_26_3_PORT.md

@@ -374,6 +374,13 @@ prototype vanilla terrain, normal authoring and most content are absent, and
 worlds should be disposable or backed up. The 1.21.1 stable release remains
 independent; issues #96–#104 stay open until the full port and validation pass.
 
+The next development slice, `1.0.1.3-alpha.1`, adds a basic Descriptive Book
+screen and server-validated binding. Naming an unbound book creates a unique
+prototype Age with a random seed; clicking the bound book's placeholder panel
+uses the acknowledged-catalog travel gate. This is not authored Page binding
+or a live destination preview. The player confirmed the Descriptive Book
+binding and travel interaction in game on 2026-10-29.
+
 ## Verification of this first slice
 
 The 1.21.1 `compileJava` and `build` tasks passed offline after the backend