Fix Stop hook loop: suppress output on typecheck success

The Stop hook was producing stdout on every run, causing Claude Code to
feed it back as context and rewake the model each turn. Now emits a
systemMessage JSON only on failure.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

.claude/settings.json

@@ -18,7 +18,8 @@
         "hooks": [
           {
             "type": "command",
-            "command": "npm run typecheck 2>&1"
+            "command": "output=$(npm run typecheck 2>&1); rc=$?; if [ $rc -ne 0 ]; then printf '{\"systemMessage\":\"TypeCheck failed:\\n%s\"}' \"$(echo \"$output\" | tail -30 | sed 's/\"/\\\\\"/g; s/$/\\\\n/' | tr -d '\\n')\"; fi",
+            "timeout": 60
           }
         ]
       }