fix(creatures): a renewed path starts from the stored point, not where the client draws the mover #608

This was generated by AI during triage.

#570 fixed the snap-back when a mover stops between creature ticks (#603, packages #61). A related gap remains when a moving bot's path is renewed instead of stopped.

emit_creature_path (module/src/creatures/tick/mod.rs) starts the new leg at the mover's stored position. Since the persist rule in #587 (advance_needs_persist, 4 yd), the stored position can lag the rendered one by up to 4 yd for an out-of-combat creature, and by up to one 500 ms tick for a Character. When the runner renews a path mid-leg (the playerbots begin() path in runner/movement.rs), the new spline starts behind the point the client shows, and the client can snap the mover back.

Done when: a path renewal mid-leg starts the new spline from the point along the old leg at the renewal time (the same stop_on_leg rule stop_where_rendered uses, including the obstruction check). A test renews a path between ticks and asserts the new spline's start equals the rendered point.

Found in the review of packages #61.