Add -u/--up and -d/--down, wired to compose-parser stub commands

Both take a required OCI images directory plus an optional compose file
name (defaulting to "compose.yaml", resolved relative to the cwd) via the
same manual two-token consumption -v/--volume already uses, just with the
second token optional. The stub commands aren't no-ops: they resolve the
images directory, load and validate the compose file through the existing
load_compose_file()/validate_compose_external_state(), and print a summary
-- confirming the CLI wiring and parser work end to end -- before logging
that actual orchestration isn't implemented yet.

Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01Gv3s5jckJKzh6JkMoi2Akz

tests/unit/test_cli_args.cpp

@@ -249,3 +249,48 @@ TEST_CASE("parse_args: --log-level sets log_level_flag_given", "[unit]") {
     REQUIRE_FALSE(with_level.exit_code.has_value());
     CHECK(with_level.args.log_level_flag_given);
 }
+
+TEST_CASE("parse_args: -u/--up defaults compose_file_name to compose.yaml when omitted", "[unit]") {
+    auto result = run_parse({"-u", "/var/lib/images"});
+    REQUIRE_FALSE(result.exit_code.has_value());
+    CHECK(result.args.mode == Mode::compose_up);
+    REQUIRE(result.args.compose_images_directory.has_value());
+    CHECK(*result.args.compose_images_directory == "/var/lib/images");
+    CHECK(result.args.compose_file_name == "compose.yaml");
+}
+
+TEST_CASE("parse_args: -u accepts an explicit second token as compose_file_name", "[unit]") {
+    auto result = run_parse({"-u", "/var/lib/images", "my-stack.yaml"});
+    REQUIRE_FALSE(result.exit_code.has_value());
+    CHECK(result.args.mode == Mode::compose_up);
+    CHECK(*result.args.compose_images_directory == "/var/lib/images");
+    CHECK(result.args.compose_file_name == "my-stack.yaml");
+}
+
+TEST_CASE("parse_args: -u doesn't swallow a following flag as compose_file_name", "[unit]") {
+    auto result = run_parse({"-u", "/var/lib/images", "--log-level", "debug"});
+    REQUIRE_FALSE(result.exit_code.has_value());
+    CHECK(result.args.mode == Mode::compose_up);
+    CHECK(*result.args.compose_images_directory == "/var/lib/images");
+    // The default, since "--log-level" looks like a flag, not a filename.
+    CHECK(result.args.compose_file_name == "compose.yaml");
+    CHECK(result.args.log_level_flag_given);
+}
+
+TEST_CASE("parse_args: -d/--down works the same way as -u/--up", "[unit]") {
+    auto default_name = run_parse({"--down", "/var/lib/images"});
+    REQUIRE_FALSE(default_name.exit_code.has_value());
+    CHECK(default_name.args.mode == Mode::compose_down);
+    CHECK(default_name.args.compose_file_name == "compose.yaml");
+
+    auto explicit_name = run_parse({"-d", "/var/lib/images", "my-stack.yaml"});
+    REQUIRE_FALSE(explicit_name.exit_code.has_value());
+    CHECK(explicit_name.args.mode == Mode::compose_down);
+    CHECK(explicit_name.args.compose_file_name == "my-stack.yaml");
+}
+
+TEST_CASE("parse_args: -u and -d together on the same command line is a parse error", "[unit]") {
+    auto result = run_parse({"-u", "/var/lib/images", "-d", "/var/lib/images"});
+    REQUIRE(result.exit_code.has_value());
+    CHECK(*result.exit_code == 1);
+}