feat: add all domain layers (dotfiles, packages, remote, containers)

- Dotfiles: models, module resolution, path resolution, link planning
- Packages: models, catalog parsing, resolution, install/remove planning
- Remote: target parsing, SSH command building
- Containers: image refs, mount resolution, container specs

All domain code is pure functions + frozen dataclasses. 88 tests.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

tests/test_domain_containers.py

@@ -0,0 +1,80 @@
+"""Tests for containers domain."""
+
+from pathlib import Path
+
+from flow.domain.containers.models import ContainerSpec, ImageRef, Mount
+from flow.domain.containers.resolution import (
+    build_container_spec,
+    container_name,
+    parse_image_ref,
+    resolve_mounts,
+)
+
+
+class TestParseImageRef:
+    def test_simple_name(self):
+        ref = parse_image_ref("devbox")
+        assert ref.registry == "registry.tomastm.com"
+        assert ref.name == "devbox"
+        assert ref.tag == "latest"
+
+    def test_with_tag(self):
+        ref = parse_image_ref("devbox:v2")
+        assert ref.tag == "v2"
+
+    def test_full_ref(self):
+        ref = parse_image_ref("ghcr.io/user/image:main")
+        assert ref.registry == "ghcr.io"
+        assert ref.name == "user/image"
+        assert ref.tag == "main"
+
+    def test_full_image_string(self):
+        ref = parse_image_ref("devbox")
+        assert ref.full == "registry.tomastm.com/devbox:latest"
+
+
+class TestContainerName:
+    def test_basic(self):
+        assert container_name("personal", "devbox") == "flow-personal-devbox"
+
+
+class TestResolveMounts:
+    def test_projects_mount(self, tmp_path):
+        projects = tmp_path / "projects"
+        projects.mkdir()
+        mounts = resolve_mounts(tmp_path, str(projects))
+        project_mounts = [m for m in mounts if m.target == "/home/user/projects"]
+        assert len(project_mounts) == 1
+
+    def test_extra_mounts(self, tmp_path):
+        mounts = resolve_mounts(
+            tmp_path, str(tmp_path),
+            extra_mounts=[{"source": str(tmp_path), "target": "/data"}],
+        )
+        extra = [m for m in mounts if m.target == "/data"]
+        assert len(extra) == 1
+
+
+class TestBuildContainerSpec:
+    def test_basic(self):
+        image = ImageRef(registry="reg", name="img", tag="v1")
+        spec = build_container_spec("personal", image, [])
+        assert spec.name == "flow-personal-img"
+        assert spec.env["DF_NAMESPACE"] == "personal"
+        assert spec.env["DF_PLATFORM"] == "container"
+
+    def test_with_mounts(self):
+        image = ImageRef(registry="reg", name="img", tag="v1")
+        mounts = [Mount(source=Path("/a"), target="/b")]
+        spec = build_container_spec("ns", image, mounts)
+        assert len(spec.mounts) == 1
+
+
+class TestMount:
+    def test_to_flag(self):
+        m = Mount(source=Path("/src"), target="/dst")
+        assert m.to_flag() == "-v /src:/dst"
+
+    def test_to_flag_readonly(self):
+        m = Mount(source=Path("/src"), target="/dst", readonly=True)
+        assert ":ro" in m.to_flag()