Theme system overhaul, UI polish, and VS2022 Dark theme

- Replaced hardcoded theme factories with JSON files + CMake build step
- Shared ThemeFieldMeta table for DRY serialization and editor UI
- Fixed live preview (auto-triggers on color change, no toggle button)
- Fixed duplicate theme entries when editing built-in themes
- Moved title bar from icon to bold "Reclass" text with View > Show Icon toggle
- MDI tabs: 24px height, unicode close button styled like TypeSelectorPopup
- Added VS2022 Dark theme with purple accent colors
- Status bar padding, removed monospace font overrides on tabs/statusbar
- Default startup opens Ball demo + Unnamed hex64 tabs

src/themes/defaults/reclass_dark.json

@@ -0,0 +1,29 @@
+{
+    "name": "Reclass Dark",
+    "background": "#1e1e1e",
+    "backgroundAlt": "#252526",
+    "surface": "#2a2d2e",
+    "border": "#3c3c3c",
+    "borderFocused": "#888888",
+    "button": "#333333",
+    "text": "#d4d4d4",
+    "textDim": "#858585",
+    "textMuted": "#585858",
+    "textFaint": "#505050",
+    "hover": "#2b2b2b",
+    "selected": "#232323",
+    "selection": "#2b2b2b",
+    "syntaxKeyword": "#569cd6",
+    "syntaxNumber": "#b5cea8",
+    "syntaxString": "#ce9178",
+    "syntaxComment": "#6a9955",
+    "syntaxPreproc": "#c586c0",
+    "syntaxType": "#4EC9B0",
+    "indHoverSpan": "#E6B450",
+    "indCmdPill": "#2a2a2a",
+    "indDataChanged": "#8fbc7a",
+    "indHintGreen": "#5a8248",
+    "markerPtr": "#f44747",
+    "markerCycle": "#e5a00d",
+    "markerError": "#7a2e2e"
+}