feat(themes): executive-ivory — the light half of the executive pair

Second exclusive pair (see 0ba1762 for the batch). Executive Ivory is
the slate boardroom at 9 AM: the night skyline traded for paper, print
and daylight. Warm ivory base (#F2F0E9), ink text (12.1:1 AAA), the
steel blue deepened to letterhead weight (#2F5FBF, 5.25:1 as text),
JetBrainsMono + slate's exact 5/12/2/10 geometry. Assets: the same
solid edge-to-edge strip identity (ink on ivory, accent underline on
the active workspace), rofi, btop, and a line-web wallpaper that
mirrors slate's geometry in silver-on-paper with sparse blue threads.

Verification: V2, same evidence set as 0ba1762 (all targeted checks
green on this tree; theme-shot VM desktop + menu viewed — strip,
underline, paper panel all render legibly; screenshots in
/nix/store/5883sqfz...theme-shot-executive-ivory). Preview is the
480x270 VM render. V3 pending per the batch HARDWARE-QUEUE entry.

Design on Fable; asset port by a Sonnet subagent from the
executive-slate sources; reviewed on Fable.

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>

themes/executive-ivory.json

@@ -0,0 +1,60 @@
+{
+  "version": 1,
+  "name": "Executive Ivory",
+  "slug": "executive-ivory",
+  "mode": "light",
+  "wallpaper": "",
+  "colors": {
+    "base": "#F2F0E9",
+    "mantle": "#DCD9CE",
+    "surface": "#E8E5DB",
+    "overlay": "#ABA898",
+    "text": "#252D3B",
+    "subtext": "#4A5568",
+    "muted": "#767E8D",
+    "accent": "#2F5FBF",
+    "accentAlt": "#46689E",
+    "good": "#3E7449",
+    "warn": "#8D6110",
+    "bad": "#A84048"
+  },
+  "border": {
+    "active": "accent",
+    "inactive": "overlay"
+  },
+  "fonts": {
+    "mono": "JetBrainsMono Nerd Font",
+    "ui": "Inter",
+    "size": 11
+  },
+  "ui": {
+    "gapsIn": 5,
+    "gapsOut": 12,
+    "borderSize": 2,
+    "rounding": 10,
+    "iconSize": 36,
+    "activeOpacity": 1.0,
+    "inactiveOpacity": 0.95,
+    "terminalOpacity": 0.96,
+    "blur": true,
+    "shadow": true
+  },
+  "ansi": [
+    "#252D3B",
+    "#A84048",
+    "#3E7449",
+    "#8D6110",
+    "#2F5FBF",
+    "#6B4FA8",
+    "#2E7D88",
+    "#F2F0E9",
+    "#767E8D",
+    "#BC5560",
+    "#4F8A5B",
+    "#A5761A",
+    "#4674D0",
+    "#7E63BE",
+    "#3D93A0",
+    "#FAF9F4"
+  ]
+}