The Phase 3 fix for #266 removed UIEntity::self which prevented
tp_dealloc from ever running. However, this also allowed Python
subclass wrappers (GameEntity, ZoneExit, etc.) to be GC'd while
the C++ entity lived on in a grid. Later access via grid.entities
returned a base Entity wrapper, losing all subclass methods.
Fix: Add UIEntity::pyobject field that holds a strong reference to
the Python wrapper. Set in init(), cleared when the entity leaves
a grid (die(), set_grid(None), collection removal). This keeps
subclass identity alive while in a grid, but allows proper GC when
the entity is removed. Added releasePyIdentity() helper called at
all grid exit points.
Regression test exercises Liber Noster patterns: subclass hierarchy,
isinstance() checks, combat mixins, tooltip/send methods, GC
survival, die(), pop(), remove(), and stress test with 20 entities.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
