Portable install: the binary installs itself; static builds on five architectures; root via sudo, doas or uid 0; every package manager; older systemd; no lsblk

- hamlab install / uninstall (internal/setup): systemd or OpenRC, elevates through
  sudo or doas, runs as the invoking user, sets or generates the password, names only
  journal groups that exist, waits for /healthz, reports an active firewalld/ufw.
  --purge and the data chown never touch a directory that isn't Ham Lab's alone.
- install.sh: curl-able bootstrap (arch detection, SHA256SUMS, offline beside the
  binaries, noexec /tmp fallback). make release builds dist/ for amd64, arm64, arm
  (ARMv6), 386, riscv64. Every build is CGO_ENABLED=0; the native one used to link glibc.
- internal/priv replaces every literal `sudo -n`: uid 0, sudo or doas.
- Updates acts on dnf, zypper, pacman and apk as well as apt; dnf shows installed versions.
- Services falls back to the plain systemctl table before systemd 246 and says so on
  hosts without systemd. Disks falls back to /sys/block without lsblk.
- Listener binds with IP_FREEBIND, so a LAN address that isn't up at boot is no failure.
- Self-update: the new build must pass `check` against the live config, is put in
  place by atomic rename, and the daemon re-execs itself (same under any supervisor).
- State and config writes are fsynced; a corrupt state.json is set aside, not fatal.
- Terminal shutdown no longer empties the saved list, so names come back after a
  restart by design rather than by winning a race.
- Config default is ~/.config/hamlab; an existing ~/apps/hamlab is still found.

Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

internal/priv/priv.go

@@ -0,0 +1,78 @@
+// Package priv is the one place that knows how this daemon gets root: it already is root,
+// or it has passwordless sudo, or passwordless doas (Alpine, some BSD-minded setups), or
+// it has nothing and the privileged features stay off.
+package priv
+
+import (
+	"context"
+	"os"
+	"os/exec"
+	"strings"
+	"sync"
+	"time"
+)
+
+var (
+	once   sync.Once
+	mode   string // "root" | "sudo" | "doas" | ""
+	prefix []string
+)
+
+func detect() {
+	if os.Geteuid() == 0 {
+		mode = "root"
+		return
+	}
+	for _, tool := range []string{"sudo", "doas"} {
+		if _, err := exec.LookPath(tool); err != nil {
+			continue
+		}
+		ctx, cancel := context.WithTimeout(context.Background(), 3*time.Second)
+		err := exec.CommandContext(ctx, tool, "-n", "true").Run()
+		cancel()
+		if err == nil {
+			mode, prefix = tool, []string{tool, "-n"}
+			return
+		}
+	}
+}
+
+// Mode reports how root is reached: "root", "sudo", "doas", or "" when it can't be.
+func Mode() string { once.Do(detect); return mode }
+
+// Available reports whether commands can be run as root without a prompt.
+func Available() bool { return Mode() != "" }
+
+// Wrap returns args prefixed so they run as root. Without privilege it returns args
+// unchanged; callers gate on Available() where that matters.
+func Wrap(args ...string) []string {
+	once.Do(detect)
+	return append(append([]string{}, prefix...), args...)
+}
+
+// AsUser returns args prefixed so they run as another user with that user's HOME.
+func AsUser(user string, args ...string) []string {
+	switch Mode() {
+	case "sudo":
+		return append([]string{"sudo", "-n", "-u", user, "-H"}, args...)
+	case "doas":
+		return append([]string{"doas", "-n", "-u", user}, args...)
+	case "root":
+		if user == "root" {
+			return args
+		}
+		// su exists everywhere (util-linux, shadow, busybox), needs no password from root
+		// and sets HOME for the target user.
+		return []string{"su", "-s", "/bin/sh", user, "-c", Quote(args)}
+	}
+	return args
+}
+
+// Quote joins args into one POSIX shell command line.
+func Quote(args []string) string {
+	q := make([]string, len(args))
+	for i, a := range args {
+		q[i] = "'" + strings.ReplaceAll(a, "'", `'\''`) + "'"
+	}
+	return strings.Join(q, " ")
+}