Constant ENTRY_IDLE_BUDGET 

pub const ENTRY_IDLE_BUDGET: Duration;

phase-521 W6 (RFC-0113 D2) — the longest park an entry asks for when every source of work can end it early: 60 s.

Not unbounded, because every port and backend must express it: FreeRTOS’s pdMS_TO_TICKS multiplies in a 32-bit TickType_t and wraps above ~71 minutes at 1 kHz, and a 32-bit Zephyr timeout wraps sooner at a high tick rate. A deadline sooner than this ends the park sooner. See Executor::entry_spin_budget.