fix(validation): restore baseline quality gates

[rochecompaan]

Summary

• resolve the repository-wide strict TypeScript baseline diagnostics with sound narrowing, safe indexed access, exact-optional contracts, and explicit overrides
• preserve existing pipeline behavior and public object shapes while correcting optional workspace, artifact, recovery, host, and callback handling
• declare typebox as a direct dependency, enable export-map-aware dependency resolution, update the shrinkwrap, and refresh the Nix npm dependency hash

This baseline repair is intentionally separate from #156.

Validation

• npm run check:types
• npm run check:architecture
• npm run build
• npm run lint
• npm test — 1,497 passed, 0 failed
• nix build .#patchmill --print-build-logs — 1,482 passing package test lines, 0 failures
• git diff --check

No new tests were added because the change is static type and dependency hygiene with no intended behavior change; the existing suite caught and verified the runtime compatibility fixes.