fix: Nemo terminal/keymap/vscode — alacritty default, CH+FR lock, code action

- dconf 00-cinnamon: add org.cinnamon+gnome.desktop.default-applications.terminal
  exec='alacritty' exec-arg='-e' so Nemo right-click → Open in Terminal works
- dconf locks/keyboard: lock input-sources/sources and terminal exec keys so
  csd-keyboard doesn't reset them to defaults on first session start
- build-live-iso.sh: add code-open wrapper script (/usr/local/bin/code-open)
  that finds 'code' in the live user's nix profile; add open-in-vscode
  Nemo action to /usr/share/nemo/actions/
- config/install.conf: add nixpkgs#vscode to NIX_USER_PACKAGES
- packages.live-desktop.list: add setxkbmap (needed by csd-keyboard to
  apply XKB keyboard layout)

iso/build-live-iso.sh

@@ -397,12 +397,31 @@ picture-options='zoom'
 [org/gnome/desktop/input-sources]
 sources=[('xkb', 'ch+fr')]
 
+[org/cinnamon/desktop/default-applications/terminal]
+exec='alacritty'
+exec-arg='-e'
+
+[org/gnome/desktop/default-applications/terminal]
+exec='alacritty'
+exec-arg='-e'
+
 [org/cinnamon/desktop/keybindings/custom-keybindings/custom0]
 name='Open Terminal'
 command='${DEFAULT_TERMINAL:-alacritty}'
 binding=['<Primary><Alt>t']
 EOF
 
+# dconf lock file — prevents the live user's session from overriding the
+# keyboard layout with an empty list on first start.
+install -d -m 0755 "$INCLUDE_DIR/etc/dconf/db/local.d/locks"
+cat > "$INCLUDE_DIR/etc/dconf/db/local.d/locks/keyboard" <<'EOF'
+/org/gnome/desktop/input-sources/sources
+/org/cinnamon/desktop/default-applications/terminal/exec
+/org/cinnamon/desktop/default-applications/terminal/exec-arg
+/org/gnome/desktop/default-applications/terminal/exec
+/org/gnome/desktop/default-applications/terminal/exec-arg
+EOF
+
 # ── 3e) Copy themes/icons/wallpapers directly into usr/share ────────────
 # (dconf compile happens inside the Docker container — see _inner-build-live.sh)
 install -d -m 0755 "$INCLUDE_DIR/usr/share/backgrounds/void-installer"
@@ -414,6 +433,45 @@ install -d -m 0755 "$INCLUDE_DIR/usr/share/themes"
 install -d -m 0755 "$INCLUDE_DIR/usr/share/icons"
 [[ -d "$OVERLAY/icons" ]] && cp -a "$OVERLAY/icons"/. "$INCLUDE_DIR/usr/share/icons/" 2>/dev/null || true
 
+# ── 3e-bis) Nemo actions ─────────────────────────────────────────────────
+install -d -m 0755 "$INCLUDE_DIR/usr/share/nemo/actions"
+install -d -m 0755 "$INCLUDE_DIR/usr/local/bin"
+
+# Wrapper script: finds 'code' in the live user's nix profile.
+# Used by the Nemo action so it doesn't need to know the nix profile path.
+cat > "$INCLUDE_DIR/usr/local/bin/code-open" <<'EOF'
+#!/bin/sh
+# Open VS Code for the given file/folder arguments.
+# Looks in the live user's nix profile first, then falls back to PATH.
+for d in "/home/live/.nix-profile/bin" /nix/var/nix/profiles/per-user/live/profile/bin \
+         /usr/local/bin /usr/bin; do
+    if [ -x "$d/code" ]; then
+        exec "$d/code" "$@"
+    fi
+done
+exec code "$@"
+EOF
+chmod 0755 "$INCLUDE_DIR/usr/local/bin/code-open"
+
+# Nemo action: Open in VS Code
+cat > "$INCLUDE_DIR/usr/share/nemo/actions/open-in-vscode.nemo_action" <<'EOF'
+[Nemo Action]
+
+Name=Open in VS _Code
+
+Comment=Open in Visual Studio Code
+
+Exec=/usr/local/bin/code-open %F
+
+Icon-Name=code
+
+Selection=Any
+
+Extensions=any;
+
+Dependencies=/usr/local/bin/code-open;
+EOF
+
 # ── 3f) first-login autostart + profile.d for the live user ─────────────
 install -d -m 0755 "$INCLUDE_DIR/etc/xdg/autostart"
 if [[ -r "$OVERLAY/first-login.sh" ]]; then