feat(theme): parchment/dark-bay/vignette shader surfaces as drop-in scenes

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

client/scripts/theme/surfaces/dark_bay.gd

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+class_name DarkBay
+extends Panel
+## Drop-in dark stripe+vignette bay backdrop. §2: presentation.
+const Palette = preload("res://scripts/theme/palette.gd")
+
+
+func _ready() -> void:
+	var m := ShaderMaterial.new()
+	m.shader = load("res://assets/theme/shaders/dark_bay.gdshader")
+	m.set_shader_parameter("stripe_a", Palette.BAY_STRIPE_A)
+	m.set_shader_parameter("stripe_b", Palette.BAY_STRIPE_B)
+	material = m

client/scripts/theme/surfaces/dark_bay.gd.uid

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+uid://24c8pl0yx8wu

client/scripts/theme/surfaces/parchment_panel.gd

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+class_name ParchmentPanel
+extends Panel
+## Drop-in parchment backdrop (mockups "Dark Bay + Parchment" motif). §2: presentation.
+const Palette = preload("res://scripts/theme/palette.gd")
+
+
+func _ready() -> void:
+	var m := ShaderMaterial.new()
+	m.shader = load("res://assets/theme/shaders/parchment.gdshader")
+	m.set_shader_parameter("top", Palette.SHEET_TOP)
+	m.set_shader_parameter("bottom", Palette.SHEET_BOTTOM)
+	material = m

client/scripts/theme/surfaces/parchment_panel.gd.uid

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+uid://cnv1r00ane2la

client/scripts/theme/surfaces/vignette_overlay.gd

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+class_name VignetteOverlay
+extends ColorRect
+## Drop-in edge-dim overlay for pause/dialogue dim. §2: presentation.
+
+
+func _ready() -> void:
+	color = Color(0, 0, 0, 0)  # base transparent; shader draws the dim
+	mouse_filter = Control.MOUSE_FILTER_IGNORE
+	var m := ShaderMaterial.new()
+	m.shader = load("res://assets/theme/shaders/vignette.gdshader")
+	material = m

client/scripts/theme/surfaces/vignette_overlay.gd.uid

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+uid://7bc7agrl6oi0