fix(audit): scope to GitHub-only and bundle CLI with esbuild

Narrow the posture audit to GitHub posture only. warden governs GitHub,
so multi-domain IaC auditing (aws/azure/k8s/docker/gcp/helm/gitlab/forgejo)
belongs to the separate blacklight app. The engine now wires only the
github CI lexicon (path-detected .github/workflows/*, github postSynthChecks).

Drop the 8 non-github lexicon dependencies; keep @intentius/chant and
@intentius/chant-lexicon-github.

Bundle the CLI with esbuild so chant's .ts source is transpiled and inlined
at build time. This fixes ERR_UNSUPPORTED_NODE_MODULES_TYPE_STRIPPING when
running dist/cli.js under plain Node. chant packages export .ts by default,
which only worked under vitest's transpiler. Convert the engine's dynamic
chant imports to static top-level imports so esbuild inlines them.

Author: lex00