Extend and embed

Maelys System integration

Understand which low-level mechanics come from Maelys System and which lifecycle duties remain in Executor.

The dependency direction is strictly:

CODE

maelys-executor -> libmaelys-sys

Maelys System never includes Executor headers or process-domain types. Executor's public header does not expose Maelys System types. Executor ABI 10 therefore remains independent of System's concrete layouts; the dependency appears only at build and final static link time.

Extracted mechanics

Executor need	Maelys System contract
monotonic and wall timestamps	`maelys_sys_monotonic_ms`, `maelys_sys_wall_ms`
owned descriptor cleanup	`maelys_sys_fd_close`
child I/O construction	`maelys_sys_pipe_cloexec`, `maelys_sys_socketpair_cloexec`
mediated-channel request write	`maelys_sys_socket_send_nosigpipe`
mediator shutdown notification	`maelys_sys_wakeup_*`

make system-integration-check inspects the unresolved symbols of libmaelys_executor.a and fails unless every contract above is genuinely consumed. Normal execution, mediated networking and shutdown tests then link a single pinned libmaelys_sys.a and exercise the composition.

Deliberately retained by Executor

posix_spawn file actions and descriptor layout;
process-group ownership, waitpid and signals;
graceful/forced bounded shutdown and terminal status mapping;
backend prepare/artifact/spawn/wait/stop/release operations;
Bubblewrap, Seatbelt, filesystem/network enforcement and receipts.

These operations carry execution-domain meaning and do not satisfy the Maelys System admission rule requiring a domain-free primitive needed by two real consumers.

The dependency is pinned to the exact commit in adapter/MAELYS_SYSTEM_PIN. The build refuses a different checkout, a modified public contract, or a non-ABI-1 header. Installed SDK archives contain both static libraries and both pkg-config files; maelys-executor.pc declares maelys-sys as a private dependency for static consumers.