feat: carve Jajce river into terrain

docs/LEARNING_ROADMAP.md

@@ -889,15 +889,29 @@ Unload/rebind state authority, stable tie order, moved anchors, reservations,
 player parity, and a deliberately far high-priority winner remain covered. See
 [Loaded Resource Discovery 01](benchmarks/LOADED_RESOURCE_DISCOVERY_01.md).
 
-The immediate next slice should pair this systems foundation with the authored
-world: sculpt the real Terrain3D river channel and waterfall shelf, rebake and
-validate navigation, then use the first larger foliage/resource pass to prove a
-bounded stable-ID anchor placement workflow alongside decorative Terrain3D
-instancing. Do not generalize the resource grid to people/buildings/events or
+The authored-watercourse slice is complete. `JajceWatercourse` now gives the
+deterministic terrain generator and both water ribbons one shared profile; the
+generated Terrain3D data contains an upper stream, raised waterfall shelf,
+plunge basin, and curved downstream channel. A matched Metal capture records
+the result, and the Terrain3D-derived navigation mesh was rebaked and validated
+against required village/resource routes.
+
+The immediate next slice should prove one bounded foliage/resource authoring
+workflow in the real world: build a restrained riverbank or forest-edge cluster
+with decorative Terrain3D/intentional instances, pair only selected harvestable
+trees or berry patches with stable-ID `ResourceNode` anchors, and verify nearby
+and farther loaded anchors remain discoverable through `ActiveWorldAdapter`.
+Keep decorative instances out of simulation state, measure the bounded visual
+cost, and do not generalize the resource grid to people/buildings/events or
 introduce active/abstract LOD before those consumers need it.
 
 Recently completed:
 
+- `Jajce River 03`: deterministic Terrain3D generation now carves the upper
+  stream, raised waterfall shelf, plunge basin, and curved downstream channel;
+  shared watercourse geometry keeps both water ribbons aligned, soft masked
+  mist replaces hard billboards, and the rebaked navigation mesh passes
+  terrain-height and runtime resource-route checks.
 - Loaded-resource spatial discovery: a resource-specific active-world grid
   preserves exact score winners and lifecycle authority while reducing the
   reviewed 1,800-anchor query from 6.45 ms to 46.94 µs.