Add Floating Islands and material-driven Age features (#45)

Keep repeated feature and material pages in authored writing, vary their resolved materials, and expose Link Panel modifier variants in creative and JEI. Remove Descriptive Book writing notes and refine Void biome selection.

docs/DESCRIPTIVE_BOOK_PRESENTATION.md

@@ -4,13 +4,13 @@ The Legacy-style front spread has the Age name and author on the left and the de
 
 The Binder records the taking player's name on the finished book; direct Age binding also records the binding player. Older books without this component display `Unknown author` rather than attributing them to whoever happens to open them. Link-Panel-only and older page-free books retain their random-Age glyph details and destination preview. On authored books, hovering the front-page name exposes the existing trait summary without filling the left page with text.
 
-The server resolves symbol display metadata from its current catalog and sends advisory grammar diagnostics with the book-opening payload. A missing data-pack symbol draws the unresolved page artwork and its original ID. An affected page displays a red `!` with the server's diagnostic on hover; separate writing-note pages show all diagnostics, including incomplete branches that the Age compiler filled. These UI notices do not alter or recompile the persisted Age plan. Symbol pages use the same bounded, runtime glyph composition as Page items and do not require Create, Ponder, or Immersive Portals.
+The server resolves symbol display metadata from its current catalog. A missing data-pack symbol draws the unresolved page artwork and its original ID. Descriptive Books do not show writing notes or grammar warning markers; grammar validation remains in the Binder and on the server when an Age is created. Opening a book never changes its persisted Age plan. Symbol pages use the same bounded, runtime glyph composition as Page items and do not require Create, Ponder, or Immersive Portals.
 
 ## Manual visual and behavior checks
 
 1. Bind a Descriptive Book with two distinct symbol pages. Open it: the front spread shows its Age name, your player name, and the link panel. Turn twice and confirm exactly one large symbol on each right page, in authored order, with no plain-text symbol description or blank trailing page.
 2. Hover the front-page name to confirm the trait summary remains accessible. Click the link panel to confirm normal travel; repeat from a lectern to check the name, panel, and page-turn layout.
 3. Open a Link-Panel-only book and confirm its existing random-Age details and destination preview still appear.
-4. In a copy of a test world, remove a data pack that supplied one authored symbol. Reopen the book: its original symbol ID should remain readable beside the unresolved artwork, and the writing notes should explain the missing definition. Restore the pack and verify the page artwork returns without changing the saved Age.
+4. In a copy of a test world, remove a data pack that supplied one authored symbol. Reopen the book: its original symbol ID should remain readable beside the unresolved artwork, with no writing-notes pages. Restore the pack and verify the page artwork returns without changing the saved Age.
 
 `./gradlew build --offline` verifies compilation and jar assembly. The visual and data-pack-removal checks require an in-game client.