frontend: deep-link via ?instance=; client/frontend default to :9090; Makefile help; v1.1.0

- cmd/frontend/web: honour ?instance=<hostname> query parameter on the
  initial scope hydration so /view/?instance=lb-ams opens the dashboard
  scoped to that maglevd. The cookie is updated on consumption; an
  unknown name still falls back to the first server via App.tsx.

- cmd/client, cmd/frontend: --server now accepts bare hostnames. A new
  internal/netutil.EnsurePort canonicalises addresses by appending
  :9090 when no port is given, with bracketing for bare IPv6 literals.
  Unit test covers the IPv4/IPv6/bracketed/already-ported permutations.

- Makefile: new self-documenting `help` target as the default rule;
  every user-facing target now carries a `## ` description that the
  awk-based help auto-extracts. fixstyle-web skips with a friendly
  message when prettier isn't installed instead of failing on npx.

Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>

internal/netutil/netutil.go

@@ -0,0 +1,32 @@
+// SPDX-License-Identifier: Apache-2.0
+
+// Package netutil holds tiny networking helpers shared across cmd/
+// binaries. Kept deliberately minimal — anything more involved than a
+// few lines belongs in its own package.
+package netutil
+
+import (
+	"net"
+	"strings"
+)
+
+// EnsurePort returns addr unchanged when it already carries a port, or
+// addr with ":<defaultPort>" appended otherwise. Bare IPv6 literals
+// ("2001:db8::1", "::1") are bracketed so the result is valid input to
+// grpc.NewClient and net.Dial. An empty addr is returned unchanged.
+func EnsurePort(addr, defaultPort string) string {
+	if addr == "" {
+		return addr
+	}
+	if _, _, err := net.SplitHostPort(addr); err == nil {
+		return addr
+	}
+	// Already-bracketed bare IPv6 ("[::1]") falls through to the plain
+	// concat at the bottom. Unbracketed IPv6 needs brackets first; we
+	// detect it by handing the literal to net.ParseIP, which only
+	// accepts the bare form (no brackets, no port).
+	if ip := net.ParseIP(addr); ip != nil && ip.To4() == nil && strings.Contains(addr, ":") {
+		return "[" + addr + "]:" + defaultPort
+	}
+	return addr + ":" + defaultPort
+}

internal/netutil/netutil_test.go

@@ -0,0 +1,35 @@
+// SPDX-License-Identifier: Apache-2.0
+
+package netutil
+
+import "testing"
+
+func TestEnsurePort(t *testing.T) {
+	const dp = "9090"
+	cases := []struct {
+		in, want string
+	}{
+		{"", ""},
+		{"chbtl2", "chbtl2:9090"},
+		{"chbtl2:9090", "chbtl2:9090"},
+		{"chbtl2:1234", "chbtl2:1234"},
+		{"lb-ams.example.com", "lb-ams.example.com:9090"},
+		{"lb-ams.example.com:9090", "lb-ams.example.com:9090"},
+		{"192.0.2.1", "192.0.2.1:9090"},
+		{"192.0.2.1:9090", "192.0.2.1:9090"},
+		{"::1", "[::1]:9090"},
+		{"2001:db8::1", "[2001:db8::1]:9090"},
+		{"[::1]:9090", "[::1]:9090"},
+		{"[2001:db8::1]:443", "[2001:db8::1]:443"},
+		// Already-bracketed but missing port: net.SplitHostPort rejects
+		// it, ParseIP rejects the bracketed textual form, so the plain
+		// concat path adds ":9090" and yields a valid host:port.
+		{"[::1]", "[::1]:9090"},
+	}
+	for _, tc := range cases {
+		got := EnsurePort(tc.in, dp)
+		if got != tc.want {
+			t.Errorf("EnsurePort(%q) = %q, want %q", tc.in, got, tc.want)
+		}
+	}
+}