Detailed Description

Generic RTOS abstraction — public header.

Exposes one set of OS_* types and os_* functions regardless of the scheduler underneath, so component code never names a kernel. Select a backend by defining exactly one of:

Macro	Backend	Header
`HF_RTOS_CMSIS`	CMSIS-RTOS2 (`osThreadNew` / `osDelay`)	`os/os_cmsis.h`
`HF_RTOS_FREERTOS`	FreeRTOS (vanilla or ESP-IDF SMP)	`os/os_freertos.h`
`HF_RTOS_THREADX`	Azure RTOS ThreadX	`os/os_threadx.h`
(none)	Bare-metal / host tests	`os/os_none.h`

Porting contract

A backend owns every kernel difference — include layout, core affinity, critical-section style, tick source. Consumers must never need a force-included compatibility header or a synthesized include directory to make a backend compile. If a kernel variant does not fit, extend its backend header; do not patch it from a build system.

Capability macros a backend must define:

os_thread_create_pinned always exists; it degrades to an unpinned create when the kernel is single-core.
os_get_current_core_id always exists; it returns 0 when single-core.

See also: os/README.md for the backend matrix and how to add one.