Start Housecarl: the logo, the wordmark and the skeleton

Housecarl will be a firewall manager for nftables, built the way Jarl and
Steward are: housecarld (a daemon with a REST API and web UI), hc (the
CLI) and SQLite.

- The logo: a carved Nordic doorway in Jarl's blue (artwork/logo.svg),
  with a small version without the carvings, lighter on dark
  backgrounds. scripts/logo.py builds the web UI's copies and
  scripts/banner.py the README banner.
- The HOUSECARL wordmark in Jarl's and Steward's angular letters, with
  new H, O, U and C (assets/brand.js), and the UI's color tokens.
- housecarld and hc print their version; the Makefile, version package,
  AGENTS.md, CHANGELOG and the design sketch (docs/design.md).

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

cmd/hc/main.go

@@ -0,0 +1,42 @@
+// Command hc is Housecarl's command line client: it will manage the
+// firewall through housecarld's API, as jarl and steward do for theirs.
+// For now it only knows its version.
+package main
+
+import (
+	"fmt"
+	"os"
+
+	"github.com/spf13/cobra"
+
+	"housecarl/internal/version"
+)
+
+func main() {
+	if err := rootCmd().Execute(); err != nil {
+		fmt.Fprintln(os.Stderr, "error:", err)
+		os.Exit(1)
+	}
+}
+
+func rootCmd() *cobra.Command {
+	root := &cobra.Command{
+		Use:   "hc",
+		Short: "Manage a Housecarl firewall",
+		Long: `hc will manage a Housecarl firewall through housecarld's API: its zones,
+address sets, rules and port forwards. It doesn't yet: Housecarl is at its
+start (docs/design.md).`,
+		SilenceUsage:  true,
+		SilenceErrors: true,
+		Version:       version.String(),
+	}
+	root.AddCommand(versionCmd())
+	return root
+}
+
+func versionCmd() *cobra.Command {
+	return &cobra.Command{
+		Use: "version", Short: "Print the version", Args: cobra.NoArgs,
+		Run: func(cmd *cobra.Command, args []string) { fmt.Println("hc", version.String()) },
+	}
+}