Add Productize operator entrypoint and setup trust

[itseffi]

Summary

• add /productize build operator route contract and bundled productize-operator reusable agent
• add setup doctor and explicit multi-agent setup opt-in
• make bundled operator discoverable before install and update docs/runtime references

Verification

• env PATH=/Users/effi/go/bin:/Users/effi/.codex/tmp/arg0/codex-arg0JnKWkU:/Users/effi/.local/bin:/Users/effi/.opencode/bin:/Users/effi/.bun/bin:/opt/homebrew/opt/postgresql@16/bin:/opt/homebrew/bin:/opt/homebrew/sbin:/usr/local/bin:/System/Cryptexes/App/usr/bin:/usr/bin:/bin:/usr/sbin:/sbin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/local/bin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/bin:/var/run/com.apple.security.cryptexd/codex.system/bootstrap/usr/appleinternal/bin:/opt/pmk/env/global/bin:/Library/Apple/usr/bin:/usr/local/share/dotnet:~/.dotnet/tools:/Applications/quarto/bin:/Users/effi/.cargo/bin:/Applications/Codex.app/Contents/Resources GOCACHE=/private/tmp/productize-go-cache GOLANGCI_LINT_CACHE=/private/tmp/productize-golangci-cache npm_config_cache=/private/tmp/productize-npm-cache make verify