tune: edge warp 5 m @12/island -> 12 m @20/island (terrain-water task 10)

Sized from measurement, not taste-first. |grad raw| at the K3/K4/K5
contours on seed 1375359975 is p50 0.00088 raw/px, so the first try (5 m,
12 undulations/island) displaced the shelf boundary a MEAN of 3.7 px with
a roughness ratio of 1.03 -- real, and invisible at map scale. At 12 m
and 20/island the boundary moves a mean 8.4 px (bench) / 9.1 px
(plateau), roughness ratio 1.09, and the outline grows the notches, coves
and peninsulas the sketch asked for.

Measured cost at 12 m (A off vs B, same seed): lowland and toe/red bands
bit-identical in both pixel count and slope -- the K2 pin holding exactly,
as designed. Foothill riser p50 0.681 -> 0.676 m/px, p90 1.445 -> 1.478,
max 3.09 -> 3.81. Bench p50 0.21 -> 0.232 (micro-relief included), still
buildable. Peaks max identical at 6.55.

Safety bound restated from "half the margin to a fixed knot" to 2/3 of
the smaller adjacent band, which is the constraint that actually matters:
the squeezed band never compresses below a third of its nominal width, so
its slope never more than triples. That puts the ceiling at 16.45 m for
the v5 knots and leaves the 12 m default real headroom if the gate says
"more".

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

Core/Scripts/ConfigManager.cs

@@ -39,10 +39,10 @@ namespace IslaApocalypse.Core // Change this if your namespace is different
 		// of OUTPUT height. ShelfEdgeVariation is the shelf-edge warp amplitude in
 		// metres of INPUT height — how far the shelf/riser boundary contour is
 		// displaced, not an elevation change; it is clamped at load time to the
-		// largest shift that keeps the curve's knots ordered. Defaults: v1, 3 m, 5 m.
+		// largest shift the curve's bands can absorb. Defaults: v1, 3 m, 12 m.
 		public static string TerrainDetail = "v1";
 		public static float ShelfReliefAmp = 3.0f;
-		public static float ShelfEdgeVariation = 5.0f;
+		public static float ShelfEdgeVariation = 12.0f;
 
 		public static void LoadConfig()
 		{

Tools/Scripts/TerrainDetailPass.cs

@@ -34,19 +34,31 @@ public static class TerrainDetailPass
 
 	// Pass B — shelf-edge variation. The amplitude is stated in metres of INPUT
 	// height (raw × 251): it is how far, in raw-height terms, a shelf boundary
-	// contour is displaced — not an output elevation change. Lateral wander on
-	// the map is that displacement divided by the local raw gradient.
-	public const float EDGE_AMP_DEFAULT_M = 5f;      // config dial: ShelfEdgeVariation (metres of input height)
-	public const float EDGE_FREQ_ISLANDS = 12f;      // ~12 undulations per island width — a handful of notches
-	public const int EDGE_SEED_OFFSET = 7507;        //   per shelf perimeter, not hundreds of teeth
-	public const float EDGE_SAFETY_FRACTION = 0.5f;  // shift ≤ half the smallest margin to a fixed knot
+	// contour is displaced — not an output elevation change. What the eye sees is
+	// the LATERAL wander, which is that displacement divided by the local raw
+	// gradient. Measured on seed 1375359975: |∇raw| at the K3/K4/K5 contours is
+	// p50 0.00088 raw/px, so 12 m of input height buys a median peak displacement
+	// of ~54 px and a mean of ~8 px along the boundary — coves and notches, which
+	// is where the developer's sketch sits. 5 m (the first try) moved the boundary
+	// a mean 3.7 px and was invisible at map scale.
+	public const float EDGE_AMP_DEFAULT_M = 12f;     // config dial: ShelfEdgeVariation (metres of input height)
+	public const float EDGE_FREQ_ISLANDS = 20f;      // ~410 px wavelength at 8K — coves and notches at the
+	public const int EDGE_SEED_OFFSET = 7507;        //   scale of the sketch, not a fringe of teeth
+
+	// The shift squeezes whichever of the foothill riser / plateau bands it moves
+	// into. Bounding it at 2/3 of the smaller band means that band never compresses
+	// below a THIRD of its nominal width — i.e. its slope never more than triples,
+	// even where peak noise lands on a boundary. That is the real constraint; knot
+	// ordering follows from it.
+	public const float EDGE_SAFETY_FRACTION = 2f / 3f;
 
 	/// <summary>
-	/// The largest per-column knot shift this preset can take while keeping the
-	/// knot set strictly ordered (K2 &lt; K3+d, K5+d &lt; K6) with margin to spare.
-	/// K1/K2/K6 never move, so the toe, the orange/red bands and the summit spike
-	/// are bit-identical whatever the warp does — which is what makes the
-	/// red-ceiling and peak-height guarantees exact rather than statistical.
+	/// The largest per-column knot shift this preset allows: bounded by the band
+	/// squeeze above, which also keeps the knot set strictly ordered
+	/// (K2 &lt; K3+d, K5+d &lt; K6) with a third of each band to spare. K1/K2/K6 never
+	/// move, so the toe, the orange/red bands and the summit spike are
+	/// bit-identical whatever the warp does — which is what makes the red-ceiling
+	/// floor and the 420 m cap exact rather than statistical.
 	/// </summary>
 	public static float MaxEdgeShift(CurveKnots k)
 	{