feat(themes): add executive-slate professional dark theme

Leveraged Nano Banana to generate a 4k functional minimalist wallpaper. Added the new preset with a solid, high-legibility waybar and flat rofi launcher.

themes/executive-slate.json

@@ -0,0 +1,43 @@
+{
+  "version": 1,
+  "name": "Executive Slate",
+  "slug": "executive-slate",
+  "mode": "dark",
+  "wallpaper": "",
+  "colors": {
+    "base": "#1A1D24",
+    "mantle": "#14161C",
+    "surface": "#232731",
+    "overlay": "#333947",
+    "text": "#D4DAE8",
+    "subtext": "#8792A6",
+    "muted": "#525A6E",
+    "accent": "#4D78CC",
+    "accentAlt": "#6C92D9",
+    "good": "#68A06B",
+    "warn": "#D19C4C",
+    "bad": "#C95F65"
+  },
+  "border": {
+    "active": "accent",
+    "inactive": "overlay"
+  },
+  "ansi": [
+    "#232731",
+    "#C95F65",
+    "#68A06B",
+    "#D19C4C",
+    "#4D78CC",
+    "#836CC9",
+    "#4C99A0",
+    "#D4DAE8",
+    "#525A6E",
+    "#D67177",
+    "#7BB57F",
+    "#E0AF5E",
+    "#6C92D9",
+    "#9A84E0",
+    "#5FABB3",
+    "#FFFFFF"
+  ]
+}