fix(doc-guardian): replace prompt hook with command hook

Prompt hooks are unreliable - Claude ignores instructions and generates
verbose analysis despite explicit FORBIDDEN rules. Command hooks guarantee
the exact output we want.

- Add notify.sh script that only outputs for config file changes
- Change hooks.json from prompt type to command type
- Script exits silently for non-config files (no blocking)

Fixes #110

Co-Authored-By: Claude Opus 4.5 <noreply@anthropic.com>

plugins/doc-guardian/hooks/notify.sh

@@ -0,0 +1,23 @@
+#!/bin/bash
+# doc-guardian notification hook
+# Outputs a single notification for config file changes, nothing otherwise
+# This is a command hook - guaranteed not to block workflow
+
+# Read tool input from stdin (JSON with file_path)
+INPUT=$(cat)
+
+# Extract file_path from JSON input
+FILE_PATH=$(echo "$INPUT" | grep -o '"file_path"[[:space:]]*:[[:space:]]*"[^"]*"' | head -1 | sed 's/.*"file_path"[[:space:]]*:[[:space:]]*"\([^"]*\)".*/\1/')
+
+# If no file_path found, exit silently
+if [ -z "$FILE_PATH" ]; then
+    exit 0
+fi
+
+# Check if file is in a config directory (commands/, agents/, skills/, hooks/)
+if echo "$FILE_PATH" | grep -qE '/(commands|agents|skills|hooks)/'; then
+    echo "[doc-guardian] Config file modified. Run /doc-sync when ready."
+fi
+
+# Exit silently for all other files (no output = no blocking)
+exit 0