iter9-numfix-a: L2/L3 数字可读性修复（甲案——数字墨族按板自适应）

- 根因：v3.5 冻结④亮墨三档（#D8ECF0 系）直画只按 L1 dungeon 验收；underdark/deep_underdark
  地板亮白筋纹归一后 p90=0.40/0.66，亮墨对亮斑 CR 1.0-1.9 融字（用户实机截图 2026-09-30 实证）
- 修法：_digit_ink_mode 按归一后地板逐像素分位数选墨族——对 p90 ≥4.5 且对均值 ≥2.0，
  亮族过选亮族否则深墨三档（青墨/赭墨/锈墨色温语义同构）；缺盘平色回退态默认深墨
- 实测（引擎口径）：dungeon 亮族 4.79/5.80 维持；underdark 深族 5.34/2.41；deep_underdark 深族 5.08/2.42
- 机检面：terrain_tile_sets_test 增三关对比断言（同一归一+选族管线+期望族表）21/21 绿
- 轻闸：冒烟 596/0+ui_input/ui/click/layout 四探针 PASS

game/tests/unit/presentation/terrain_tile_sets_test.gd

@@ -36,6 +36,7 @@ func _init() -> void:
 	_check("前置：board_gen 词表非空（%d 型）" % types.size(), types.size() > 0)
 	_test_set_completeness(board_dir, types)
 	_test_hue_domains(board_dir)
+	_test_digit_ink_modes(board_dir, types)
 	if _failures > 0:
 		push_error("[terrain_tile_sets_test] %d/%d 项失败" % [_failures, _checks])
 		quit(1)
@@ -128,3 +129,40 @@ func _load_stats(board_dir: String, fname: String, top_half: bool) -> Dictionary
 	if n_v == 0 or n_h == 0:
 		return {}
 	return {"h": h_sum / n_h, "v": v_sum / n_v}
+
+
+# 数字墨族按板自适应对比断言（L2/L3 亮瓦融字缺陷修复 2026-10-01——甲案机检面）：
+# 每个图型走 BoardView 同一归一+测光+选族管线（禁测试侧另写算法），断言：
+# ①所选墨族对 p90 亮斑 ≥4.5 且对均值 ≥2.5（双门槛，同 _digit_ink_mode 判据常量）
+# ②期望族面：dungeon=亮族（样张 v3.5 冻结④原样）；underdark/deep_underdark=深族（亮白筋纹 p95
+#   0.66–0.77 上亮墨 CR 1.0–1.9 融字实证）——期望表防「选族逻辑被顺手改坏」回归
+func _test_digit_ink_modes(board_dir: String, types: Array) -> void:
+	var expect_dark := {"dungeon": false, "underdark": true, "deep_underdark": true}
+	var variants: int = int(BoardViewScript.TILE_FLOOR_VARIANTS)
+	for bt in types:
+		var lumas: Array = []
+		var readable := true
+		for i in range(1, variants + 1):
+			var p := board_dir.path_join("terrain_floor_%s_%d.png" % [String(bt), i])
+			if not FileAccess.file_exists(p):
+				readable = false
+				break
+			var tex: Texture2D = ImageTexture.create_from_image(Image.load_from_file(p))
+			BoardViewScript._normalize_floor_luma(tex, 0.10, lumas)
+		if not readable:
+			_check("图型 %s 数字墨族断言样本可读" % String(bt), false)
+			continue
+		var mode: Dictionary = BoardViewScript._digit_ink_mode(lumas)
+		var dark: bool = bool(mode["dark"])
+		var cr_p90 := float(mode["cr_p90_bright"]) if not dark else float(mode["cr_p90_dark"])
+		var cr_mean := float(mode["cr_mean_bright"]) if not dark else float(mode["cr_mean_dark"])
+		var family := "亮墨族" if not dark else "深墨族"
+		_check("图型 %s 所选%s 对 p90 ≥%.1f（实测 %.2f）" % [String(bt), family,
+			float(BoardViewScript.DIGIT_INK_CR_P90), cr_p90],
+			cr_p90 >= float(BoardViewScript.DIGIT_INK_CR_P90))
+		_check("图型 %s 所选%s 对均值 ≥%.1f（实测 %.2f）" % [String(bt), family,
+			float(BoardViewScript.DIGIT_INK_CR_MEAN), cr_mean],
+			cr_mean >= float(BoardViewScript.DIGIT_INK_CR_MEAN))
+		if expect_dark.has(bt):
+			_check("图型 %s 墨族期望=%s（实测=%s）" % [String(bt),
+				"深族" if bool(expect_dark[bt]) else "亮族", family], dark == bool(expect_dark[bt]))