Add uv and a rootless Docker runtime on NixOS hosts

uv joins the CLI package list. Docker's daemon is now actually managed
on NixOS hosts too, in rootless mode (per-user systemd service, no
docker-group root-equivalent access), rather than leaving the runtime
entirely externally-managed as before -- the already-installed docker
CLI picks it up automatically via DOCKER_HOST. This is a documented,
narrow exception to developer-environment's client-only tools policy;
kubectl and awscli2 remain unaffected.

Archives add-uv-and-docker-runtime and syncs the new container-runtime
capability plus the narrowed developer-environment requirement into
the main specs.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01HngxrvqEzq8oBEBDtrYJyB

1 files changed, 21 insertions, 0 deletions

diff --git a/openspec/specs/container-runtime/spec.md b/openspec/specs/container-runtime/spec.md
new file mode 100644
index 0000000..0b07f92
--- /dev/null
+++ b/openspec/specs/container-runtime/spec.md
@@ -0,0 +1,21 @@
+# container-runtime Specification
+
+## Purpose
+
+Provides a working, unprivileged Docker container runtime on every NixOS host built from this flake, so the already-provisioned Docker CLI tooling has a daemon to talk to without a separately-managed installation step.
+
+## Requirements
+
+### Requirement: A rootless Docker daemon runs on every NixOS host
+Every NixOS host built from this flake's shared system module SHALL run a Docker daemon in rootless mode (as the user's own account, not as root), without requiring per-host opt-in.
+
+#### Scenario: Daemon available after boot
+- **WHEN** a NixOS host built from this flake's shared system module finishes booting and the user logs in
+- **THEN** a Docker daemon is running under that user's own account, not as root
+
+### Requirement: The Docker CLI connects to the rootless daemon without manual configuration
+A user on a NixOS host built from this flake's shared system module SHALL be able to run Docker CLI commands (e.g. `docker run`, `docker build`) against the rootless daemon without manually setting `DOCKER_HOST` or other connection configuration.
+
+#### Scenario: Docker command works out of the box
+- **WHEN** a user runs a `docker` CLI command on a NixOS host built from this flake's shared system module
+- **THEN** the command reaches the rootless daemon and executes, without the user having exported `DOCKER_HOST` or written any Docker connection config themselves