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/boot/initramfs-hook-my-custom-logo

@@ -0,0 +1,29 @@
+#!/bin/sh
+# Bakes a real, dereferenced copy of the NexusOS Plymouth theme into the
+# initramfs. The theme files live in nexus-core and are exposed at
+# /usr/share/plymouth/themes/my-custom-logo via a symlink into /home, which
+# the stock initramfs plymouth hook copies verbatim -> it dangles at early
+# boot (before /home is mounted) and Plymouth falls back to text mode.
+# This hook runs after the stock "plymouth" hook and replaces that dangling
+# symlink with the actual theme files.
+
+PREREQS="plymouth"
+prereqs() { echo "$PREREQS"; }
+
+case "$1" in
+	prereqs)
+		prereqs
+		exit 0
+		;;
+esac
+
+. /usr/share/initramfs-tools/hook-functions
+
+THEME_SRC="/home/jon/nexus-core/assets/boot/my-custom-logo"
+THEME_DEST="${DESTDIR}/usr/share/plymouth/themes/my-custom-logo"
+
+[ -d "${THEME_SRC}" ] || exit 0
+
+rm -rf "${THEME_DEST}"
+mkdir -p "${THEME_DEST}"
+cp -aL "${THEME_SRC}/." "${THEME_DEST}/"