# K13 — EventGroup and coordinated state

K13 provides a typed `EventMask<Enum>` and `EventGroup<Enum>` over static
FreeRTOS event-group storage. Wait policy is explicit (`any`/`all`) and clear
policy is explicit (`keep`/`clear_on_exit`). `WaitResult` retains the snapshot
returned by the kernel and evaluates it against the requested policy.

Three workers publish UART, GPIO and APP readiness bits. The coordinator then
executes a deterministic state sequence:

```text
wait all, keep          -> snapshot 0x7, current 0x7
clear GPIO              -> clear returns 0x7, current 0x5
wait all, 3 ticks       -> timeout snapshot 0x5, unsatisfied
wait any UART|APP, clear-> snapshot 0x5, current 0x0
```

Setting UART twice leaves the mask at `0x1`, proving an event bit is idempotent
state and not an occurrence counter.

## Build

```sh
make check
```

## Debug

```gdb
b event_group_debug_checkpoint
p g_coordinator_state_seen
p g_worker_set_result
p g_uart_repeat_mask
p/x g_all_snapshot
p/x g_mask_after_gpio_clear
p/x g_timeout_snapshot
p g_timeout_ticks
p/x g_any_snapshot
p/x g_final_mask
p g_event_group_pass
```

## Scope boundary

Bits coordinate state but carry neither payload nor occurrence count. A
clear-on-exit policy can race with other consumers unless designed explicitly.
The ISR form of setting bits is not a direct edit of the event group; FreeRTOS
defers that operation through the timer service path, which is outside this
task-context card.