🎨 Differentiate tool window background from editor background

Official Darcula keeps the editor (#2B2B2B) visibly darker than tool
window/panel chrome (#3C3F41); official IntelliJ Light keeps the editor
(pure white) visibly lighter than its panel chrome (#F2F2F2). Our non-Islands
variants used the exact same shade for both, so the Project view, Structure
view, and Git Log blended flat into the editor with no visual separation.

- Dracula, Dracula Colorful: tool window content (and Tree, which the
  Project/Structure/Git panels render through) now uses the lighter
  secondaryBackground instead of matching the editor's primaryBackground.
- Dracula Alucard: tool window content now uses the brighter primaryBackground
  instead of matching the editor's secondaryBackground.

Left the tool window header's existing active/inactive distinction alone
since it already differs correctly and touching it risked collapsing that
back to one color.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013zoiYJou155vxSB1XE5WiH

Author: WhiteVermouth

src/main/resources/themes/Dracula.theme.json

@@ -271,7 +271,7 @@
       "buttonColor": "primaryForeground"
     },
     "ToolWindow": {
-      "background": "primaryBackground",
+      "background": "secondaryBackground",
       "Button": {
         "selectedBackground": "selectionBackground",
         "hoverBackground": "hoverBackground"
@@ -288,7 +288,7 @@
       }
     },
     "Tree": {
-      "background": "primaryBackground",
+      "background": "secondaryBackground",
       "modifiedItemForeground": "accentColor",
       "selectionBackground": "selectionBackground",
       "selectionInactiveBackground": "selectionInactiveBackground",

src/main/resources/themes/DraculaAlucard.theme.json

@@ -266,7 +266,7 @@
       "buttonColor": "primaryForeground"
     },
     "ToolWindow": {
-      "background": "secondaryBackground",
+      "background": "primaryBackground",
       "Button": {
         "selectedForeground": "primaryForeground",
         "selectedBackground": "selectionBackground",

src/main/resources/themes/DraculaColorful.theme.json

@@ -271,7 +271,7 @@
       "buttonColor": "primaryForeground"
     },
     "ToolWindow": {
-      "background": "primaryBackground",
+      "background": "secondaryBackground",
       "Button": {
         "selectedBackground": "selectionBackground",
         "hoverBackground": "hoverBackground"
@@ -288,7 +288,7 @@
       }
     },
     "Tree": {
-      "background": "primaryBackground",
+      "background": "secondaryBackground",
       "modifiedItemForeground": "accentColor",
       "selectionBackground": "selectionBackground",
       "selectionInactiveBackground": "selectionInactiveBackground",