Sable Gravity 0.6.0 test16

Built on the working test13 Sable OBB collision path.

Changes from test15:

• never imports Sable-mutated world deltaMovement back into local velocity; removes tilted-floor drift;
• uses Sable local floor contact as the authoritative ground state;
• keeps creative flight independent from stale world-axis onGround state;
• captures flight ascend/descend against the exact previous post-tick velocity, so ship rotation cannot become fake acceleration;
• updates walk animation directly from the actual local displacement because cancelled Player.travel never reaches vanilla calculateEntityAnimation;
• replaces Sable/vanilla sneak edge backoff with a full local plot-space floor query;
• leaves Entity.bb axis-aligned only for Minecraft broadphase. It is no longer used as the source of local ground, flight or sneak behaviour.