feat(valkey): initial stable release v0.9.0

Valkey (Redis-compatible) client component with launcher lifecycle and health check integration.

What's included:
- Config with Addrs, Password, SelectDB, CacheSizeEachConn (env-driven)
- Provider interface exposing native valkey-go Client() directly (no wrapper)
- Component interface: launcher.Component + health.Checkable + Provider
- New(logger, cfg) constructor for lifecycle registration via lc.Append
- Health check via PING at LevelDegraded priority
- Graceful shutdown calling client.Close() in OnStop

Tested-via: todo-api POC integration
Reviewed-against: docs/adr/

valkey.go

@@ -0,0 +1,92 @@
+package valkey
+
+import (
+	"context"
+	"fmt"
+
+	vk "github.com/valkey-io/valkey-go"
+
+	"code.nochebuena.dev/go/health"
+	"code.nochebuena.dev/go/launcher"
+	"code.nochebuena.dev/go/logz"
+)
+
+// Provider is the minimal interface for consumers that only need the valkey client.
+type Provider interface {
+	Client() vk.Client
+}
+
+// Component adds lifecycle management and health check to Provider.
+type Component interface {
+	launcher.Component
+	health.Checkable
+	Provider
+}
+
+// Config holds Valkey connection settings.
+type Config struct {
+	Addrs             []string `env:"VK_ADDRS,required"  envSeparator:","`
+	Password          string   `env:"VK_PASSWORD"`
+	SelectDB          int      `env:"VK_DB"              envDefault:"0"`
+	CacheSizeEachConn int      `env:"VK_CLIENT_CACHE_MB" envDefault:"0"` // MB; 0 = disable
+}
+
+type vkComponent struct {
+	cfg    Config
+	logger logz.Logger
+	client vk.Client
+}
+
+// New returns a valkey Component. Call lc.Append(vk) to manage its lifecycle.
+func New(logger logz.Logger, cfg Config) Component {
+	return &vkComponent{cfg: cfg, logger: logger}
+}
+
+func (v *vkComponent) OnInit() error {
+	opts := vk.ClientOption{
+		InitAddress: v.cfg.Addrs,
+		Password:    v.cfg.Password,
+		SelectDB:    v.cfg.SelectDB,
+	}
+	if v.cfg.CacheSizeEachConn > 0 {
+		opts.CacheSizeEachConn = v.cfg.CacheSizeEachConn * 1024 * 1024
+	}
+	client, err := vk.NewClient(opts)
+	if err != nil {
+		return fmt.Errorf("valkey: failed to create client: %w", err)
+	}
+	v.client = client
+	return nil
+}
+
+func (v *vkComponent) OnStart() error {
+	v.logger.Info("valkey: verifying connection")
+	if v.client == nil {
+		return fmt.Errorf("valkey: client not initialized")
+	}
+	if err := v.client.Do(context.Background(), v.client.B().Ping().Build()).Error(); err != nil {
+		return fmt.Errorf("valkey: ping failed: %w", err)
+	}
+	v.logger.Info("valkey: connected")
+	return nil
+}
+
+func (v *vkComponent) OnStop() error {
+	v.logger.Info("valkey: closing client")
+	if v.client != nil {
+		v.client.Close()
+	}
+	return nil
+}
+
+func (v *vkComponent) Client() vk.Client { return v.client }
+
+func (v *vkComponent) HealthCheck(ctx context.Context) error {
+	if v.client == nil {
+		return fmt.Errorf("valkey: client not initialized")
+	}
+	return v.client.Do(ctx, v.client.B().Ping().Build()).Error()
+}
+
+func (v *vkComponent) Name() string          { return "valkey" }
+func (v *vkComponent) Priority() health.Level { return health.LevelDegraded }