Function tick_spawners 

pub fn tick_spawners<'a>(
    ctx: &mut PipelineContext<'a>,
    dt: f32,
) -> FrameVec<'a, DueSpawn>

Advance every Spawner’s clock by dt and return the spawns now due, in frame scratch.

A spawner emits one copy per whole interval elapsed (so a long frame that crosses several intervals catches up), at the spawner entity’s own Transform. A non-positive interval is inert (never spawns). A zero lifetime means the copy is not auto-removed; otherwise it carries that countdown.