feat: enhance workspace dock, reorganize menus, fix Reclass Dark theme

- Workspace dock: show member count per type, expandable child rows
  (Type Name format, Hex padding filtered), search/filter box with
  recursive matching, collapsed by default, double-click navigates
  to member in editor
- Menu reorganization: Import/Export submenus, new Tools menu (Type
  Aliases, MCP Server, Options), Data Source moved to View, renamed
  Unload→Close Project, Unsplit→Remove Split, Current Tab Source→
  Data Source
- View menu: add Relative Offsets toggle (persisted, applies to all
  editors and new splits)
- Fix Reclass Dark theme: hover/selected colors were identical to
  background (#1e1e1e), now #2a2a2a/#2a2d2e for visible contrast
- Dim MDI tab text via QPalette::WindowText (Fusion ignores CSS color)
- Remove dead QProxyStyle tab handlers (never called for QMdiArea)

src/themes/defaults/reclass_dark.json

@@ -10,8 +10,8 @@
     "textDim": "#858585",
     "textMuted": "#585858",
     "textFaint": "#505050",
-    "hover": "#1e1e1e",
-    "selected": "#1e1e1e",
+    "hover": "#2a2a2a",
+    "selected": "#2a2d2e",
     "selection": "#2b2b2b",
     "syntaxKeyword": "#569cd6",
     "syntaxNumber": "#b5cea8",