cmd/hi: add integration test runner CLI tool (#2648)

* cmd/hi: add integration test runner CLI tool

Add a new CLI tool 'hi' for running headscale integration tests
with Docker automation. The tool replaces manual Docker command
composition with an automated solution.

Features:
- Run integration tests in golang:1.24 containers
- Docker context detection (supports colima and other contexts)
- Test isolation with unique run IDs and isolated control_logs
- Automatic Docker image pulling and container management
- Comprehensive cleanup operations for containers, networks, images
- Docker volume caching for Go modules
- Verbose logging and detailed test artifact reporting
- Support for PostgreSQL/SQLite selection and various test flags

Usage: go run ./cmd/hi run TestPingAllByIP --verbose

The tool uses creachadair/command and flax for CLI parsing and
provides cleanup subcommands for Docker resource management.

Updates flake.nix vendorHash for new Go dependencies.

* ci: update integration tests to use hi CLI tool

Replace manual Docker command composition in GitHub Actions
workflow with the new hi CLI tool for running integration tests.

Changes:
- Replace complex docker run command with simple 'go run ./cmd/hi run'
- Remove manual environment variable setup (handled by hi tool)
- Update artifact paths for new timestamped log directory structure
- Simplify command from 15+ lines to 3 lines
- Maintain all existing functionality (postgres/sqlite, timeout, test patterns)

The hi tool automatically handles Docker context detection, container
management, volume mounting, and environment variable setup that was
previously done manually in the workflow.

* makefile: remove test integration

Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>

---------

Signed-off-by: Kristoffer Dalby <kristoffer@tailscale.com>

cmd/hi/main.go

@@ -0,0 +1,93 @@
+package main
+
+import (
+	"context"
+	"os"
+
+	"github.com/creachadair/command"
+	"github.com/creachadair/flax"
+)
+
+var runConfig RunConfig
+
+func main() {
+	root := command.C{
+		Name: "hi",
+		Help: "Headscale Integration test runner",
+		Commands: []*command.C{
+			{
+				Name:     "run",
+				Help:     "Run integration tests",
+				Usage:    "run [test-pattern] [flags]",
+				SetFlags: command.Flags(flax.MustBind, &runConfig),
+				Run:      runIntegrationTest,
+			},
+			{
+				Name: "doctor",
+				Help: "Check system requirements for running integration tests",
+				Run: func(env *command.Env) error {
+					return runDoctorCheck(env.Context())
+				},
+			},
+			{
+				Name: "clean",
+				Help: "Clean Docker resources",
+				Commands: []*command.C{
+					{
+						Name: "networks",
+						Help: "Prune unused Docker networks",
+						Run: func(env *command.Env) error {
+							return pruneDockerNetworks(env.Context())
+						},
+					},
+					{
+						Name: "images",
+						Help: "Clean old test images",
+						Run: func(env *command.Env) error {
+							return cleanOldImages(env.Context())
+						},
+					},
+					{
+						Name: "containers",
+						Help: "Kill all test containers",
+						Run: func(env *command.Env) error {
+							return killTestContainers(env.Context())
+						},
+					},
+					{
+						Name: "cache",
+						Help: "Clean Go module cache volume",
+						Run: func(env *command.Env) error {
+							return cleanCacheVolume(env.Context())
+						},
+					},
+					{
+						Name: "all",
+						Help: "Run all cleanup operations",
+						Run: func(env *command.Env) error {
+							return cleanAll(env.Context())
+						},
+					},
+				},
+			},
+			command.HelpCommand(nil),
+		},
+	}
+
+	env := root.NewEnv(nil).MergeFlags(true)
+	command.RunOrFail(env, os.Args[1:])
+}
+
+func cleanAll(ctx context.Context) error {
+	if err := killTestContainers(ctx); err != nil {
+		return err
+	}
+	if err := pruneDockerNetworks(ctx); err != nil {
+		return err
+	}
+	if err := cleanOldImages(ctx); err != nil {
+		return err
+	}
+
+	return cleanCacheVolume(ctx)
+}