rlg-test vs rlg vs assertables

Test utilities for downstream consumers of rlg. Capture log records emitted inside a test scope and assert on them with the `assert_logged!` macro.

A near-lock-free structured logging library for Rust. Sub-microsecond ingestion via a 65k-slot ring buffer (LMAX Disruptor pattern), deferred formatting, and native OS sinks (`os_log` on macOS via `syslog(3)`, `journald` on Linux). 14 output formats including JSON, MCP, OTLP, ECS, GELF, CEF, and Logfmt.

Assertables: assert macros for better testing, debugging, quality assurance, and runtime reliability.