log.nx

log.nx -- structured logging with levels. Five-level hierarchy (TRACE < DEBUG < INFO < WARN < ERROR). Output goes to stderr (fd 2) so stdout stays clean for pipe/ redirect workflows. Each line is prefixed with a level tag + RFC 3339 timestamp + caller-supplied module name. Format: [LEVEL] <timestamp> <module>: <message> e.g. [INFO] 2026-04-21T10:30:42Z http: serving / (200) Used by: any service that needs operational visibility without pulling in a real logging framework. Pairs with timefmt.nx for the timestamp. Invariants: L1 Output is line-oriented (one line per call); LF appended even if caller's message lacks one. L2 Below-threshold calls are CHEAP -- short-circuit early before any formatting work. L3 Multi-thread safe at the SYSCALL level (sys_write is atomic up to PIPE_BUF on POSIX); concurrent log calls never interleave at the byte level for short lines. L4 No allocations on the hot path; uses a single sys_mmap buffer reused across calls.