v1.12.4

Remediation of an independent code audit (2026-06-10 Round 2). All five findings
were documentation drift — no code defect. Round 1's code/security fixes were
re-confirmed intact.

Fixed

• Install snippets pinned to the current release. The SwiftPM dependency
  examples in README.md (from: "1.4.0") and the DocC Getting Started
  article (from: "1.3.0") now use from: "1.12.3", so new consumers pick up
  the audited cancellation, sandbox, memory-limit, and documentation fixes
  instead of a pre-remediation baseline.
• Configuration reference corrected (docs/index.md). The reference wrongly
  claimed only vmMemoryLimit carried an initializer default; all five
  LuaEngineConfiguration.init parameters default. The sample signature now
  shows every default and adds the cooperativeCancellation option.
• Testing guide aligned to current CI topology (TESTING.md). Replaced the
  stale test-yams-off / test-tomlkit-on job descriptions with the unified
  data-driven test-toggles job, documented the required docs (DocC) gate,
  corrected the all-tests dependency list, and fixed the quick-test
  description (the --quick script enables all three sibling-clone optional
  dependencies, not the default dependency set).