Lock asset pipeline to free sources

Docs/Art/AssetLicenses.md

@@ -5,8 +5,8 @@ before it is used in a playable map, packaged demo, screenshot, or trailer.
 
 Allowed default sources:
 
-- Fab assets explicitly marked free or otherwise purchased/owned for this
-  project.
+- Fab assets explicitly marked free. Paid Fab assets are blocked unless Nathan
+  explicitly approves a purchase in a later task.
 - Quixel/Megascans assets available under the current Epic/Unreal terms for
   this project.
 - CC0 or public-domain assets.
@@ -30,6 +30,16 @@ Expected subfolders:
 - `Processed`: assets imported, optimized, renamed, and verified.
 - `Rejected`: assets that should not be used.
 
+## Free-Only Acquisition Gate
+
+Until Nathan explicitly approves a paid purchase, every third-party asset must
+have `Cost` recorded as `Free`, `$0`, `0`, or `N/A` for project-owned/internal
+assets. Do not use "purchased", "paid", a dollar amount above zero, or blank
+cost values in the register.
+
+Any asset with uncertain cost, marketplace bundle requirements, subscription
+requirements, or unclear entitlement belongs in `Rejected` until reviewed.
+
 ## Naming Policy
 
 Use project-readable names before import: