feat: strengthen water and foreground silhouettes

- Upgrade river shader with multi-layer UV flow, fresnel edges, foam highlights, and specular sparkle
- Upgrade waterfall shader with dual-band scrolling, distinct foam contrast, and rim transparency
- Widen river (8m) and waterfall (8m) for greater visual presence
- Increase waterfall mist particles to 72 with wider spread and longer lifetime
- Add fortress crenellations (10), three turrets, and prominent ridge banner for readable skyline silhouette
- Remove duplicate banner nodes from JajceWorld instance (now owned by FortressBlockout scene)
- Update BUILD_IN_PUBLIC_PLAN and LEARNING_ROADMAP to reflect completion

docs/LEARNING_ROADMAP.md

@@ -689,6 +689,10 @@ Recently completed:
   authored path strips that reveal the active village task loop.
 - Landmark and work-site silhouette props make the ridge landmark, pantry,
   guard, study, and rest sites easier to identify without debug labels.
+- Water and foreground silhouettes strengthened: river/waterfall shaders with
+  multi-layer UV flow, fresnel edges, foam highlights, and sparkle; wider river
+  and waterfall; fortress with crenellations, three turrets, and prominent
+  ridge banner.
 
 This order strengthens the simulation while regularly producing visible
 progress suitable for public development updates.