The agent-network code under test lives in this branch, so the e2e should
exercise it rather than a frozen published release. Flip the harness
default: combined/proxy/client are now built from their in-repo
Dockerfiles (combined/Dockerfile.multistage, proxy/Dockerfile.multistage,
e2e/harness/Dockerfile.client) under local tags. Pulling a published image
stays available by setting NB_E2E_*_IMAGE to a registry reference.
Builds now go through buildx --load so the Dockerfile cache mounts are
honored and the result is loaded for testcontainers. The CI workflow adds
a container-driver builder and a local layer cache (NB_E2E_BUILDX_CACHE)
persisted via actions/cache, which caches the base/apt/dep-download layers
across runs. The Go compile still re-runs each time, as BuildKit mount
caches cannot be exported to the GitHub cache.
Vertex (Anthropic-on-Vertex) doesn't share the chat/messages wire shapes:
the model travels in a rawPredict path and the proxy mints the service
account's OAuth token. Add a Vertex client method that posts
/v1/projects/<project>/locations/<region>/publishers/anthropic/models/<model>:rawPredict
with the Vertex anthropic_version body, and wire it into the matrix as a
path-routed provider (created without a models array). It is keyed off
GOOGLE_VERTEX_SA_BASE64 + GOOGLE_VERTEX_PROJECT (region defaults to
"global", model to a pinned claude snapshot, both overridable).
Also bump the e2e workflow runner to ubuntu-latest and add the Vertex
secrets.
The e2e suite (build tag `e2e`) stands up the combined server + proxy +
client in Docker and drives live chat-completions, so it is slow and needs
provider credentials. Gate it out of normal CI (it already is, via the
build tag) and run it on demand via workflow_dispatch. Provider scenarios
skip when their secret is unset, so it degrades gracefully.
