build: untrack packaging until the crate it packages exists

The previous commit swept in flake.nix, nix/, and a CI workflow alongside a
docs change. The crate they package is not committed, so `nix flake check`
had nothing to build and CI failed on push.

Files remain on disk; they return with the Cargo manifest and sources in one
coherent commit. Every commit on main should build.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01QzRc44KbA3wfYYKFF9UDMa
agent-session-id: cdf2c185-eeb3-4a4d-8ce0-52885f145cac
agent-tool: Claude Code
agent-tool-version: 2.1.215
agent-model: claude-opus-4-8
agent-runtime-profile: /nix/store/acr8a3l2v366jgmwiq8xdrhgz1py0db5-coding-agent-runtime-profile/share/coding-agents/profile.json
agent-skills-manifest: /nix/store/sj1v5j91h8v8d1w9lca4040302lwrd6v-agent-skills-corpus/share/agent-skills/manifest.json
tooling-profile: dotfiles@unknown-dirty

Author: schickling-assistant