apply_snapshot() now reads stationary_ticks and zone_id directly from
the server snapshot when present (D-020 compliance). Client-side
accumulation and tile lookup retained as deprecated fallbacks until
the server populates these fields. Protocol.gd extended with decode
paths and TODO markers for the server team.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>
SceneHelper class for gdUnit4: load scenes into test tree with
assert_node_exists, assert_signal_emitted, get_node_at helpers.
14 tests for GameState.apply_snapshot() covering v2+ fields.
Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>