feat(P02): HCL config file parsing — internal/config package (REQ-054)

New internal/config package: Config struct (HCL tags), Load(paths...),
MergeOverrides(flags, env) with flag>env>file>default precedence (D-039).
No package-level state (AD-023). --config persistent flag on root command;
daemon uses cfg.ListenAddr when flag at default. 11 config tests + 2 cli tests.

---ci---
project: orca
phase: 2
milestone: v0.7
status: verify
requirements:
  covered: [REQ-054]
  partial: []
---/ci---

internal/cli/root.go

@@ -1,13 +1,18 @@
 package cli
 
 import (
+	"context"
 	"encoding/json"
 	"fmt"
 	"os"
 
 	"github.com/spf13/cobra"
+
+	"git.cloudinit.dev/coreci/orca/internal/config"
 )
 
+type configCtxKey struct{}
+
 var (
 	version   = "0.1.0-dev"
 	gitCommit = "unknown"
@@ -33,6 +38,13 @@ over feature richness.`,
 				return fmt.Errorf("set ORCA_HOME for --system: %w", err)
 			}
 		}
+		if configPath != "" {
+			cfg, err := config.Load(configPath)
+			if err != nil {
+				return fmt.Errorf("load config %s: %w", configPath, err)
+			}
+			cmd.SetContext(context.WithValue(cmd.Context(), configCtxKey{}, cfg))
+		}
 		return nil
 	},
 }
@@ -40,11 +52,20 @@ over feature richness.`,
 var (
 	jsonOutput      bool
 	systemNamespace bool
+	configPath      string
 )
 
 func init() {
 	rootCmd.PersistentFlags().BoolVar(&jsonOutput, "json", false, "output in JSON format")
 	rootCmd.PersistentFlags().BoolVar(&systemNamespace, "system", false, "use system-level namespace root (/root/.orca) instead of user-level (~/.orca)")
+	rootCmd.PersistentFlags().StringVar(&configPath, "config", "", "path to config.hcl (overrides ~/.orca/config.hcl)")
+}
+
+func configFromCtx(ctx context.Context) *config.Config {
+	if v, ok := ctx.Value(configCtxKey{}).(*config.Config); ok {
+		return v
+	}
+	return nil
 }
 
 func Execute() error {