M6.16: Unified hybrid species grid + codex-styled hover popover

StepSpecies hybrid mode now uses one grid combining sire-clade species
(under a "SIRE — <Clade>" eyebrow) and dam-clade species (under
"DAM — <Clade>"). Cards are click-to-select like the purebred path —
since clades are guaranteed disjoint by StepClade's parent-conflict
rule, the lineage is implicit from the species' clade and no per-card
toggles are needed.

Hover popover now picks up the codex theme: parchment Bg2 panel with a
gild border, rounded 14px corners, and soft drop shadow; H3 display
serif title, mono Eyebrow tag, CardBody description. Detriment popovers
swap to a 3px seal-red border via the panel_detriment stylebox override
(replaces the old red Modulate hack).

Theme propagation fix: CanvasLayer breaks Godot's Control theme
inheritance, so the popup was rendering on Godot defaults. _Ready
defers a lookup of the parent Control's theme and assigns it directly
to the popup so the codex parchment + Cormorant/CrimsonPro fonts
actually resolve.

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

Theriapolis.Godot/UI/CodexTheme.cs

@@ -106,12 +106,19 @@ public static class CodexTheme
         cardSelected.ShadowOffset = new Vector2(0, 14);
         theme.SetStylebox("panel_selected", "Card", cardSelected);
 
-        // Popover frame — gild border + soft shadow. Matches .trait-hint.
+        // Popover frame — gild border + soft shadow + rounded corners.
+        // Matches .trait-hint, with a softer corner radius than the rest of
+        // the codex (cards/buttons use 2px sharp) so the floating reveal
+        // reads as a friendlier secondary surface.
         theme.SetTypeVariation("CodexPopover", "PanelContainer");
         var popover = new StyleBoxFlat
         {
             BgColor = p.Bg2,
             BorderColor = p.Gild,
+            CornerRadiusTopLeft = 14,
+            CornerRadiusTopRight = 14,
+            CornerRadiusBottomLeft = 14,
+            CornerRadiusBottomRight = 14,
             ContentMarginLeft = 16,
             ContentMarginRight = 16,
             ContentMarginTop = 14,
@@ -120,11 +127,14 @@ public static class CodexTheme
             ShadowSize = 18,
             ShadowOffset = new Vector2(0, 12),
         };
-        popover.SetBorderWidthAll(1);
+        popover.SetBorderWidthAll(2);
         theme.SetStylebox("panel", "CodexPopover", popover);
 
+        // Detriment swap — seal-red border drawn at 3px so the warning reads
+        // unambiguously against the parchment bg even at a glance.
         var popoverDetriment = (StyleBoxFlat)popover.Duplicate();
         popoverDetriment.BorderColor = p.Seal;
+        popoverDetriment.SetBorderWidthAll(3);
         theme.SetStylebox("panel_detriment", "CodexPopover", popoverDetriment);
 
         // Pill — small trait/skill chip. Mirrors .trait-chips .t-name from