Convert lecterns into Rivencraft book stands

docs/PORTING.md

@@ -46,7 +46,8 @@ the symbol grammar is introduced.
 - [x] Nearby landing search and clear failure messages.
 - [x] Descriptive Book identity and Age reference components.
 - [ ] Return-link creation as part of Descriptive Book travel.
-- [ ] Lectern/book-stand interaction.
+- [x] Lectern-to-Book-Stand conversion, displayed book, activation, removal,
+  persistence, and drops.
 - [ ] Automated in-game tests for binding, persistence, and travel.
 
 The temporary shapeless Linking Book recipe makes the linking subsystem easy
@@ -57,6 +58,17 @@ Age references use UUIDs rather than dimension keys. Milestone 3 will own the
 mapping from that stable identity to server data and a runtime dimension. This
 keeps saved books valid if an Age is migrated or regenerated.
 
+Vanilla lecterns accept extensible item tags when inserting books, but their
+block entity still validates only vanilla writable and written books. To avoid
+an invalid lectern state, inserting a Rivencraft book converts the lectern into
+a visually compatible Rivencraft Book Stand. Removing the book converts it
+back.
+
+Mystcraft Legacy did not impose an item cooldown when linking. Rivencraft's
+initial cooldown used Minecraft's item-type cooldown system, which delayed all
+Linking Book stacks at once. Version 0.1.3 removes that cooldown to match the
+legacy behavior.
+
 ## Version policy
 
 Versions follow `x.y.z`: