M6.2: Step V Abilities — drag-drop assignment + roll/auto-assign

Per GODOT_PORTING_GUIDE.md §7, the highest-risk piece in the wizard.
Three reusable widgets + the orchestrating step.

Scenes/Widgets/AbilityToken.cs:
  Draggable Control with Value + Origin metadata. _GetDragData returns
  a Dictionary payload {kind, value, from, ability, idx} per guide
  §7.1. MouseFilter = Pass so clicks propagate to the parent slot
  for the click-to-return affordance (later removed; see commit body).
  Drag preview is a dimmed duplicate.

Scenes/Widgets/AbilitySlot.cs:
  PanelContainer drop target per guide §7.2. Accepts any
  ability_value payload via _CanDropData / _DropData and emits
  Dropped(payload). Each slot owns one ability id (STR/DEX/CON/INT/
  WIS/CHA).

Scenes/Widgets/AbilityPool.cs:
  HBoxContainer drop target per guide §7.3. Accepts only slot→pool
  drops (returning an assigned value to the pool); pool→pool drops
  are no-ops.

Scenes/Steps/StepStats.cs:
  Direct port of StepStats in steps.jsx per guide §7.4. Standard
  array (default) and roll-4d6-drop-lowest method tabs; Reroll
  button visible in roll mode; Auto Assign sorts the remaining pool
  descending and places the largest values into empty slots ordered
  by class.PrimaryAbility. Three drag-drop cases (pool→slot,
  slot→slot swap, slot→pool) all delegate to a single Patch call,
  then the entire token tree rebuilds from the new draft state on
  the Changed signal — handlers don't reparent anything manually.

Issues hit during development and resolved before commit:
  - Initial click-to-return on slot pre-empted drag-from-slot every
    time (the GuiInput fired on mouse-down, before Godot detected
    the drag). Removed click-to-return — drag is the canonical
    interaction; that matches the React prototype anyway.
  - Token MouseFilter = Stop blocked clicks from reaching the slot
    layer; switched to Pass which still works as a drag source.
  - Refresh() teardown + rebuild reset the parent ScrollContainer's
    scroll to 0 every drop. CallDeferred / SetDeferred / CreateTimer
    all raced because layout settles over multiple frames; the fix
    that worked was capturing scroll position pre-rebuild and
    restoring in _Process the next frame.

Wizard.cs:
  StepTypes[5] = typeof(StepStats); the Abilities step is now
  reachable. (StepTypes[1..4, 6..7] still null — coming in M6.3+.)

Verified: all three drag scenarios + click handling + auto-assign
+ method switch + reroll work; scroll position holds across drops.

Closes M6.2. Next per guide §12: M6.3 — popover system (TraitChip +
shared PopoverLayer) before adding more easy card-grid steps.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Theriapolis.Godot/Scenes/Widgets/AbilityPool.cs

@@ -0,0 +1,37 @@
+using Godot;
+
+namespace Theriapolis.GodotHost.Scenes.Widgets;
+
+/// <summary>
+/// Container for unassigned AbilityToken children. Per
+/// GODOT_PORTING_GUIDE.md §7.3, accepts only slot→pool drops (returning
+/// an assigned value to the pool); pool→pool drops are no-ops. The step
+/// consumes <see cref="Dropped"/> and mutates CharacterDraft.StatPool /
+/// StatAssign in one call so the inevitable refresh re-creates tokens
+/// in the right places.
+/// </summary>
+public partial class AbilityPool : HBoxContainer
+{
+    [Signal] public delegate void DroppedEventHandler(Godot.Collections.Dictionary payload);
+
+    public override void _Ready()
+    {
+        AddThemeConstantOverride("separation", 8);
+        MouseFilter = MouseFilterEnum.Stop;
+        CustomMinimumSize = new Vector2(0, 64);
+    }
+
+    public override bool _CanDropData(Vector2 atPosition, Variant data)
+    {
+        if (data.VariantType != Variant.Type.Dictionary) return false;
+        var d = data.AsGodotDictionary();
+        if (!d.ContainsKey("kind") || d["kind"].AsString() != "ability_value") return false;
+        // Only slot→pool drops are meaningful; pool→pool is a no-op.
+        return d.ContainsKey("from") && d["from"].AsString() == "slot";
+    }
+
+    public override void _DropData(Vector2 atPosition, Variant data)
+    {
+        EmitSignal(SignalName.Dropped, data);
+    }
+}

Theriapolis.Godot/Scenes/Widgets/AbilitySlot.cs

@@ -0,0 +1,40 @@
+using Godot;
+
+namespace Theriapolis.GodotHost.Scenes.Widgets;
+
+/// <summary>
+/// Drop target for ability assignment. Per GODOT_PORTING_GUIDE.md §7.2:
+/// accepts any drag payload tagged "ability_value" and emits
+/// <see cref="Dropped"/> with the payload so the step orchestrates the
+/// state change centrally. Visual content (the AbilityToken when filled,
+/// or a placeholder dash when empty) is set by the step on every refresh.
+///
+/// Each slot owns exactly one ability id (STR/DEX/CON/INT/WIS/CHA). On
+/// click of a filled slot, returns the value to the pool (synthesised
+/// slot→pool payload) — matches the React prototype's "click to unbind"
+/// affordance from <c>steps.jsx</c>.
+/// </summary>
+public partial class AbilitySlot : PanelContainer
+{
+    [Signal] public delegate void DroppedEventHandler(Godot.Collections.Dictionary payload);
+
+    [Export] public string Ability { get; set; } = "STR";
+
+    public override void _Ready()
+    {
+        CustomMinimumSize = new Vector2(56, 56);
+        MouseFilter = MouseFilterEnum.Stop;
+    }
+
+    public override bool _CanDropData(Vector2 atPosition, Variant data)
+    {
+        if (data.VariantType != Variant.Type.Dictionary) return false;
+        var d = data.AsGodotDictionary();
+        return d.ContainsKey("kind") && d["kind"].AsString() == "ability_value";
+    }
+
+    public override void _DropData(Vector2 atPosition, Variant data)
+    {
+        EmitSignal(SignalName.Dropped, data);
+    }
+}

Theriapolis.Godot/Scenes/Widgets/AbilityToken.cs

@@ -0,0 +1,71 @@
+using Godot;
+
+namespace Theriapolis.GodotHost.Scenes.Widgets;
+
+/// <summary>
+/// Draggable ability-score token. Replaces the React prototype's
+/// <c>.die</c> + filled <c>.slot</c> in <c>steps.jsx</c> per
+/// GODOT_PORTING_GUIDE.md §7.1. Shows the int value as a centered
+/// label; <c>_GetDragData</c> returns a Dictionary payload describing
+/// where the token came from so the step can mutate CharacterDraft
+/// accordingly.
+///
+/// Tokens are owned by either an AbilityPool (Origin == "pool",
+/// OriginPoolIdx set) or an AbilitySlot (Origin == "slot",
+/// OriginAbility set). Dropping a token rebuilds the StepStats UI from
+/// the new draft state — token instances are short-lived.
+/// </summary>
+public partial class AbilityToken : PanelContainer
+{
+    [Export] public int Value { get; set; }
+    [Export] public string Origin { get; set; } = "pool";
+    [Export] public string OriginAbility { get; set; } = "";
+    [Export] public int OriginPoolIdx { get; set; } = -1;
+
+    public override void _Ready()
+    {
+        CustomMinimumSize = new Vector2(56, 56);
+        // PASS so clicks propagate up to the parent AbilitySlot's GuiInput
+        // handler (click-to-return). Drag detection still triggers on the
+        // deepest non-IGNORE Control under the cursor, so PASS works for
+        // _GetDragData too.
+        MouseFilter = MouseFilterEnum.Pass;
+
+        var label = new Label
+        {
+            Text = Value.ToString(),
+            HorizontalAlignment = HorizontalAlignment.Center,
+            VerticalAlignment = VerticalAlignment.Center,
+            MouseFilter = MouseFilterEnum.Ignore,
+        };
+        label.AddThemeFontSizeOverride("font_size", 22);
+        AddChild(label);
+    }
+
+    public override Variant _GetDragData(Vector2 atPosition)
+    {
+        // Drag preview — a dimmed duplicate of the token.
+        var preview = new Panel { CustomMinimumSize = new Vector2(56, 56) };
+        var lbl = new Label
+        {
+            Text = Value.ToString(),
+            HorizontalAlignment = HorizontalAlignment.Center,
+            VerticalAlignment = VerticalAlignment.Center,
+        };
+        lbl.AddThemeFontSizeOverride("font_size", 22);
+        lbl.AnchorRight = 1f;
+        lbl.AnchorBottom = 1f;
+        preview.AddChild(lbl);
+        preview.Modulate = new Color(1, 1, 1, 0.85f);
+        SetDragPreview(preview);
+
+        return new Godot.Collections.Dictionary
+        {
+            { "kind", "ability_value" },
+            { "value", Value },
+            { "from", Origin },
+            { "ability", OriginAbility },
+            { "idx", OriginPoolIdx },
+        };
+    }
+}