Close automatable P2 test gaps with mocks and httptest integration.

Add container/podman exec mocks, BITS/curl HiddenRun coverage, WinRM/GPO/systemd deploy-plan httptest, and a 3-hop discover-spread Playwright stub chain.

agent/miner/runtime_detect_test.go

@@ -0,0 +1,91 @@
+package miner
+
+import (
+	"os/exec"
+	"runtime"
+	"testing"
+)
+
+func mockVersionOKCmd(_ string, args ...string) *exec.Cmd {
+	if runtime.GOOS == "windows" {
+		if len(args) >= 2 && args[0] == "version" && args[1] == "--format" {
+			return exec.Command("cmd", "/c", "echo", "24.0.1")
+		}
+		return exec.Command("cmd", "/c", "exit", "0")
+	}
+	if len(args) >= 2 && args[0] == "version" && args[1] == "--format" {
+		return exec.Command("sh", "-c", "echo 24.0.1")
+	}
+	return exec.Command("true")
+}
+
+func mockVersionPodmanCmd(_ string, args ...string) *exec.Cmd {
+	if runtime.GOOS == "windows" {
+		if len(args) >= 2 && args[0] == "version" && args[1] == "--format" {
+			return exec.Command("cmd", "/c", "echo", "4.9.0")
+		}
+		return exec.Command("cmd", "/c", "exit", "0")
+	}
+	if len(args) >= 2 && args[0] == "version" && args[1] == "--format" {
+		return exec.Command("sh", "-c", "echo 4.9.0")
+	}
+	return exec.Command("true")
+}
+
+func TestDetectContainerRuntimePrefersDocker(t *testing.T) {
+	SetContainerRuntimeProbes(
+		func(name string) (string, error) {
+			if name == "docker" {
+				return "/usr/bin/docker", nil
+			}
+			if name == "podman" {
+				return "/usr/bin/podman", nil
+			}
+			return "", exec.ErrNotFound
+		},
+		mockVersionOKCmd,
+	)
+	defer SetContainerRuntimeProbes(nil, nil)
+
+	rt := DetectContainerRuntime()
+	if !rt.Available || rt.CLI != "docker" {
+		t.Fatalf("runtime=%+v want docker", rt)
+	}
+	if rt.Version != "24.0.1" {
+		t.Fatalf("version=%q", rt.Version)
+	}
+}
+
+func TestDetectContainerRuntimeFallsBackToPodman(t *testing.T) {
+	SetContainerRuntimeProbes(
+		func(name string) (string, error) {
+			if name == "podman" {
+				return "/usr/bin/podman", nil
+			}
+			return "", exec.ErrNotFound
+		},
+		mockVersionPodmanCmd,
+	)
+	defer SetContainerRuntimeProbes(nil, nil)
+
+	rt := DetectContainerRuntime()
+	if !rt.Available || rt.CLI != "podman" {
+		t.Fatalf("runtime=%+v want podman", rt)
+	}
+	if rt.Version != "4.9.0" {
+		t.Fatalf("version=%q", rt.Version)
+	}
+}
+
+func TestDetectContainerRuntimeUnavailable(t *testing.T) {
+	SetContainerRuntimeProbes(
+		func(string) (string, error) { return "", exec.ErrNotFound },
+		nil,
+	)
+	defer SetContainerRuntimeProbes(nil, nil)
+
+	rt := DetectContainerRuntime()
+	if rt.Available || rt.CLI != "" {
+		t.Fatalf("runtime=%+v want unavailable", rt)
+	}
+}