feat: add PostToolUse hook to auto-validate marketplace.json on edit

When marketplace-dev is installed, any Write/Edit to a marketplace.json
automatically runs `claude plugin validate` and reports pass/fail.
Users get instant feedback without remembering to validate manually.

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

.claude-plugin/marketplace.json

@@ -960,7 +960,20 @@
       ],
       "skills": [
         "./marketplace-dev"
-      ]
+      ],
+      "hooks": {
+        "PostToolUse": [
+          {
+            "matcher": "Write|Edit",
+            "hooks": [
+              {
+                "type": "command",
+                "command": "${CLAUDE_PLUGIN_ROOT}/scripts/post_edit_validate.sh"
+              }
+            ]
+          }
+        ]
+      }
     }
   ]
 }

marketplace-dev/scripts/post_edit_validate.sh

@@ -0,0 +1,32 @@
+#!/usr/bin/env bash
+# PostToolUse hook: auto-validate marketplace.json after Write/Edit
+# Checks if the edited file is marketplace.json, runs validation if so.
+
+set -euo pipefail
+
+# Read tool use details from stdin
+INPUT=$(cat)
+
+# Check if the edited file is marketplace.json
+FILE_PATH=$(echo "$INPUT" | python3 -c "
+import json, sys
+try:
+    data = json.load(sys.stdin)
+    path = data.get('tool_input', {}).get('file_path', '')
+    print(path)
+except:
+    print('')
+" 2>/dev/null)
+
+if [[ "$FILE_PATH" == *"marketplace.json"* ]]; then
+    MARKETPLACE_DIR=$(dirname "$(dirname "$FILE_PATH")")
+    if [[ -f "$FILE_PATH" ]]; then
+        RESULT=$(cd "$MARKETPLACE_DIR" && claude plugin validate . 2>&1) || true
+        if echo "$RESULT" | grep -q "Validation passed"; then
+            echo '{"result": "marketplace.json validated ✔"}'
+        else
+            ERRORS=$(echo "$RESULT" | grep -v "^$" | head -5)
+            echo "{\"result\": \"marketplace.json validation FAILED:\\n$ERRORS\"}"
+        fi
+    fi
+fi