Plugin Parity Drift Detector

Lisa reimplements some curated third-party Claude plugins as Lisa-native skills so the behavior reaches agents that can't load the Claude plugin (Codex, agy, Copilot). Each such skill is version-pinned to the upstream plugin it mirrors. When upstream advances, the Lisa reimplementation silently falls behind. This skill detects that drift deterministically.

It is the empirical core of the parity subsystem (issue #1059) and is designed to run in CI. The sibling skills are analyze-plugin (plans parity work) and implement-plugin-parity (executes an approved plan, including stamping the synced-from pins this detector reads).

The synced-from pin grammar

A Lisa-native skill that reimplements an upstream plugin carries a synced-from pin in addition to the frontmatter every skill requires (name, description, allowed-tools; note $ARGUMENTS is not substituted in skills):