Kudzu 0.16.13 - Route Artifact Explanations

Adds kudzu explain --route <route> --json to trace one exact emitted route from authored source and semantic ownership through capability selection and runtime, handler, chunk, style, and Worker byte reasons. Reports bounded deterministic JSON with raw/gzip bytes and hashes, structured missing-route diagnostics, and explicit zero-JavaScript explanations while reusing the existing artifact graph and adding no browser bytes.\n\nAlso publishes create-kudzu@0.1.138 targeting @kudzujs/core@^0.16.13.