chore: remove accidental core dumps and ignore core.*

The pre-commit hooks segfault under this workspace's ROS-polluted
LD_LIBRARY_PATH, dumping core.* files that were accidentally committed via
git add -A. Remove them and gitignore the pattern.

Author: YuanYuYuan

.gitignore

@@ -79,3 +79,6 @@ crates/hiroz-msgs/python/uv.lock
 # Cached nix dev shell environment (generated by sandbox.nu)
 .state/
 site/
+
+# crash dumps from pre-commit segfaults (ROS LD_LIBRARY_PATH glibc mismatch)
+core.*