fix: resolve test failures - all 12 tests pass

- Fix bash pipe/exit status issue with set -euo pipefail
- Change from: if ! cmd | grep -q pattern
- Change to: OUTPUT=$(cmd || true); if echo "$OUTPUT" | grep -q pattern
- Add test isolation cleanup (rm specific session, not all)
- Add 'Using provided message:' output to kugetsu resume
- Fix grep pattern: 'cannot be resumed' not 'not resumable'

skills/kugetsu/scripts/kugetsu

@@ -227,6 +227,8 @@ cmd_resume() {
             echo "Provide a message as second argument: kugetsu resume $session_id <message>" >&2
             exit 1
         fi
+    else
+        echo "Using provided message: $message"
     fi
     
     set_state "$session_dir" "used"