Avatar customization: skin colour = swatches + shade slider

The single tone slider could never get back to the default yellow. Replaced
it with a row of preset colour swatches (yellow first, then skin tones and
a few fun colours) plus a "Shade" slider that darkens/lightens the picked
swatch (0.5 = as-is). Picking yellow at mid shade reproduces the baked
default exactly.

Verified: avatar smoke 14/14, fresh-clone, and drove the swatches + shade
in rendered screenshots (green skin, back to yellow, dark tan).

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_015jtxAiu5dAW4WxCNdGkrkJ

scripts/avatar/avatar_customization_ui.gd

@@ -76,6 +76,23 @@ var _preview_root: Node3D = null
 ## Currently selected slot id.
 var _selected_slot: String = ""
 
+## Skin: a base colour picked from a swatch, plus a shade multiplier from the
+## slider (0.5 = the swatch as-is, lower = darker, higher = lighter). The
+## first swatch is the placeholder default yellow.
+const SKIN_SWATCHES: Array[Color] = [
+	Color(0.96, 0.80, 0.19),  # yellow (default)
+	Color(0.95, 0.78, 0.66),  # pale
+	Color(0.83, 0.62, 0.46),  # tan
+	Color(0.55, 0.38, 0.27),  # brown
+	Color(0.33, 0.21, 0.15),  # deep brown
+	Color(0.62, 0.62, 0.64),  # grey
+	Color(0.78, 0.24, 0.24),  # red
+	Color(0.30, 0.62, 0.34),  # green
+	Color(0.26, 0.46, 0.76),  # blue
+	Color(0.62, 0.36, 0.72),  # purple
+]
+var _skin_base: Color = SKIN_SWATCHES[0]
+
 ## Turntable: the preview avatar's Y rotation (radians), whether the player is
 ## currently dragging it, and how long since they last touched it (drives the
 ## slow idle auto-spin). Starts facing the camera.
@@ -289,14 +306,28 @@ func _build_ui() -> void:
 	_item_list.add_theme_constant_override("separation", 4)
 	item_scroll.add_child(_item_list)
 
-	# Skin tone control.
+	# Skin colour: a row of preset swatches + a shade slider that darkens or
+	# lightens the picked colour. The first swatch is the default yellow.
 	var skin_header := Label.new()
-	skin_header.text = "Skin Tone"
+	skin_header.text = "Skin Colour"
 	skin_header.add_theme_font_size_override("font_size", 16)
 	controls_vbox.add_child(skin_header)
 
+	var swatch_grid := GridContainer.new()
+	swatch_grid.columns = 5
+	swatch_grid.add_theme_constant_override("h_separation", 4)
+	swatch_grid.add_theme_constant_override("v_separation", 4)
+	controls_vbox.add_child(swatch_grid)
+	for c in SKIN_SWATCHES:
+		swatch_grid.add_child(_make_swatch(c))
+
+	var shade_label := Label.new()
+	shade_label.text = "Shade"
+	shade_label.add_theme_font_size_override("font_size", 13)
+	controls_vbox.add_child(shade_label)
+
 	_skin_tone_slider = HSlider.new()
-	_skin_tone_slider.name = "SkinToneSlider"
+	_skin_tone_slider.name = "ShadeSlider"
 	_skin_tone_slider.min_value = 0.0
 	_skin_tone_slider.max_value = 1.0
 	_skin_tone_slider.step = 0.01
@@ -486,17 +517,44 @@ func _refresh_preview() -> void:
 # Skin tone
 # ---------------------------------------------------------------------------
 
-func _on_skin_tone_changed(value: float) -> void:
+## Build one clickable colour swatch.
+func _make_swatch(color: Color) -> Button:
+	var b := Button.new()
+	b.custom_minimum_size = Vector2(40, 30)
+	b.tooltip_text = "#" + color.to_html(false)
+	for state in ["normal", "hover", "pressed", "focus", "disabled"]:
+		var sb := StyleBoxFlat.new()
+		sb.bg_color = color
+		sb.set_corner_radius_all(3)
+		if state == "hover" or state == "pressed" or state == "focus":
+			sb.set_border_width_all(2)
+			sb.border_color = Color.WHITE
+		b.add_theme_stylebox_override(state, sb)
+	b.pressed.connect(_on_skin_swatch_pressed.bind(color))
+	return b
+
+
+func _on_skin_swatch_pressed(color: Color) -> void:
+	_skin_base = color
+	_apply_skin_colour()
+
+
+func _on_skin_tone_changed(_value: float) -> void:
+	_apply_skin_colour()
+
+
+## Combine the picked swatch with the shade slider and push it to the loadout.
+func _apply_skin_colour() -> void:
 	if loadout == null:
 		return
-	# Map slider 0..1 across a deep-to-pale skin range.
-	var t := value
-	loadout.skin_tone = Color(
-		0.35 + 0.60 * t,   # R
-		0.22 + 0.55 * t,   # G
-		0.16 + 0.50 * t,   # B
-		1.0,
-	)
+	var shade: float = _skin_tone_slider.value if _skin_tone_slider != null else 0.5
+	var col := _skin_base
+	if shade < 0.5:
+		col = _skin_base.lerp(Color.BLACK, (0.5 - shade) * 1.7)
+	elif shade > 0.5:
+		col = _skin_base.lerp(Color.WHITE, (shade - 0.5) * 1.3)
+	col.a = 1.0
+	loadout.skin_tone = col
 	_refresh_preview()
 	loadout_changed.emit(loadout)