Initial commit: NexusOS project + desktop theme baseline

Captures the known-good state after theme consolidation and
consistency reconciliation:
- NexusOS GTK/xfwm4/icon theme assets (assets/themes, management/Mint-Y-Nexus)
- Tightened right-click menus, visible separators, no menu icons
- assets/themes/install-theme.sh: idempotent restore of all wiring
  (symlinks, xfconf xsettings+xfwm4, GTK 3/4 settings.ini)
- .gitignore excludes venv/ollama/models/runtime/db

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

assets/themes/NexusOS-icons-src/places/folder-home.svg

@@ -0,0 +1,18 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<svg xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink" width="128" height="128" viewBox="0 0 128 128">
+  <!-- Back of folder: tab + body silhouette in green -->
+  <path d="M 14 24 Q 14 20 18 20 L 50 20 Q 53 20 55 22 L 62 30
+           L 110 30 Q 114 30 114 34 L 114 110 Q 114 114 110 114
+           L 18 114 Q 14 114 14 110 Z" fill="#8cc63f"/>
+  <!-- White inner lip stripe -->
+  <rect x="14" y="36" width="100" height="3" fill="#f2f2f2"/>
+  <!-- Front face: deep purple body -->
+  <path d="M 14 39 L 114 39 L 114 110 Q 114 114 110 114
+           L 18 114 Q 14 114 14 110 Z" fill="#5e0066"/>
+  <!-- Top-edge highlight on the front face -->
+  <rect x="14" y="39" width="100" height="2" fill="#88008f"/>
+  <!-- House silhouette -->
+  <path d="M 64 56 L 88 76 L 84 76 L 84 96 L 70 96 L 70 84
+           L 58 84 L 58 96 L 44 96 L 44 76 L 40 76 Z"
+        fill="#f2f2f2"/>
+</svg>