Context

Part of #667. Derived from the 2026-06-13 analysis: monitoring declares [1.0.0] (2026-04-16) but has NO v1.0.0 tag (only v0.1.0); develop is 15 commits ahead of main (and v0.1.0 is 107 commits behind HEAD).

Preconditions

• common v1.0.0 tag landed (Track ecosystem-wide v1.0 API stabilization readiness common_system#639)
• monitoring error-code remap landed (the monitoring remap issue)

Scope / Acceptance Criteria

• Correct stale metrics in README.md (:44,520,581 "37/37 tests passing" -> actual ~1166 cases) and docs/PRODUCTION_QUALITY.{md,kr.md} before the cut
• Reconcile CHANGELOG [Unreleased] (feat(collectors): implement or remove test-only stub collectors #690 stub removals) into the release line
• Release-merge develop -> main; cut an annotated, GPG/SSH-signed v1.0.0 tag; enable tag protection; gh release create
• Verify vcpkg portfile SHA512; update vcpkg-registry baseline
• Close Prepare monitoring_system for v1.0 release #667