fix: block humanlayer:create_handoff from being installed

Skip the create_handoff command during humanlayer plugin installation
and explicitly remove it if previously installed.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

home/roles/development/default.nix

@@ -98,6 +98,9 @@ in
       rm -f ~/.claude/commands/humanlayer:* 2>/dev/null || true
       rm -f ~/.claude/agents/humanlayer:* 2>/dev/null || true
 
+      # Remove explicitly blocked commands that may have been installed previously
+      rm -f ~/.claude/commands/humanlayer:create_handoff.md 2>/dev/null || true
+
       # Create directories if they don't exist
       mkdir -p ~/.claude/commands
       mkdir -p ~/.claude/agents
@@ -106,6 +109,12 @@ in
       for file in ${claudePluginsRepo}/humanlayer/commands/*.md; do
         if [ -f "$file" ]; then
           filename=$(basename "$file" .md)
+
+          # Skip blocked commands
+          case "$filename" in
+            create_handoff) continue ;;
+          esac
+
           dest="$HOME/.claude/commands/humanlayer:''${filename}.md"
           rm -f "$dest" 2>/dev/null || true