feat(ui): the stipple says WHERE the ground is broken, not just that it is (T-1194)

RimWorld's technique 4, the reference this ticket names, works by CONTRAST: the
Rockies and Appalachians carry dense hatching and the Great Plains carry none.
Ferrath's Global carried an even wash of dots over every landmass instead —
texture present, information absent.

The cause was a constant measured on the wrong rung. RUGGEDNESS_FULL_SCALE_Q = 4
comes from Region ("d4 2.38"), but the elev_q path it gates only ever RUNS at the
orbital rungs, where relief_q is flat and the stipple falls back to it. Ferrath
Global measures a mean 1-cell elev_q gradient of 0.99, so a coherent 4-cell
baseline reaches ~4 and saturates the constant exactly: every land cell read as
fully rugged.

It now normalizes against the canvas's own measured gradient — the same
self-calibrating shape T-1240 gave the hillshade, and for the same reason: one
constant cannot serve rungs whose sample spacing differs by four orders of
magnitude. A contrast curve rides on top, because even unsaturated the linear
reading puts ordinary ground mid-range and paints grain everywhere.

Measured on Global, before -> after: 1,679 -> 1,900 distinct colours, 145.90 ->
147.39 lum spread, and the pale uplands now stipple visibly denser than the
lowlands beside them.

Recorded because it cost two wrong turns: I first guessed saturation, then
talked myself out of it after measuring a 1-CELL gradient (0.99) against a full
scale meant for the 4-CELL baseline, and shipped a contrast curve alone — which
measurably did nothing (1,679 -> 1,698), because a curve cannot separate values
already clamped to 1.0. The gamma is kept; it does its job now that there is a
range to curve. The elev_q gradient joins relief_q's in the capture readout, so
the next person tuning this can read the number instead of guessing at it.

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

client/tests/visual_capture.gd

@@ -339,7 +339,7 @@ func _log_atlas_view_transform(tree_root: Node, scenario_name: String) -> void:
 				"visual_capture: view-transform[%s] rung=%s world_center=%s held_extent=%s "
 				+ "canvas_position=%s canvas_scale=%s footprint_px=%s canvas_cells=%dx%d "
 				+ "courses=%d runs=%d longest=%.1fpx drawn=%d settlements=%d "
-				+ "planes=%s relief_grad=%.2f"
+				+ "planes=%s relief_grad=%.2f elev_grad=%.2f"
 			)
 			% [
 				scenario_name,
@@ -358,6 +358,7 @@ func _log_atlas_view_transform(tree_root: Node, scenario_name: String) -> void:
 				int(summary.get("settlement_count", 0)),
 				str(summary.get("plane_variety", {})),
 				float(summary.get("relief_gradient", 0.0)),
+				float(summary.get("elev_gradient", 0.0)),
 			]
 		)
 	)