feat(ci): add CLI binary builds and tip release to publish workflow

Build cross-platform nemoclaw CLI binaries (Linux musl static + macOS
aarch64 via osxcross) and publish them as a rolling 'tip' pre-release
on GitHub Releases.

New jobs: build-cli-linux, build-cli-macos, release-tip.
Existing container/wheel jobs commented out for branch testing.

Closes #108

Author: drew