subagenttasks

cwc-engineering: mac-toolchain (typed doctor) + preview-layout-verify skills

DONE 2026-07-03. (1) mac-toolchain: the darwin/zsh/Homebrew environment missing from the durable-toolchain-doctor/install family — closed-schema toolchain.json (id/kind/purpose/fixes/check/install/gate, every entry citing a real dated failure: No-Chrome-binary-for-devtools, CERTIFICATE_VERIFY_FAILED, zsh no-matches aborts, sccache bypass) + stdlib-only validate.py (NoReturn-typed failures, unknown fields rejected, --doctor runs checks verbatim). Live first run: 2/6 present (jq, rsvg-convert — doctor corrected my own wrong assumptions), 4 missing with exact gated fixes (chrome + certifi + 2 zshrc lines await operator approval — system mutations are operator-gated). Type-safety contract per operator directive: the model copies validator output verbatim, never free-recalls install strings — recorded as standing memory typed-manifests-over-recall. (2) preview-layout-verify: the Claude Preview harness workflow that verified deck v9, packaged with the three invariant measurements and all four harness gotchas (reload-in-own-eval, scrollTo instant, black-screenshot-after-scroll, inspect-over-screenshot). Both registered in the plugin README.