Add config command structure with subcommands

Implement the foundation for configuration management in the CLI including:

- Main `config` command grouped under "system"
- Five subcommands: `set`, `get`, `unset`, `describe`, and `list`
- Shell completion for configuration keys across relevant subcommands
- Configuration description system with type, description, example, and default fields

Examples:
- `construct config describe defaults.agent` - Get detailed information about a config key
- `construct config set <key> <value>` - Set configuration value
- `construct config get <key>` - Get configuration value
- `construct config list` - List all configuration values
- `construct config unset <key>` - Remove configuration value

Author: Furisto

frontend/cli/cmd/config.go

@@ -0,0 +1,26 @@
+package cmd
+
+import (
+	"github.com/spf13/cobra"
+)
+
+var configOptions = []string{
+	"task.default-agent",
+	"agent.default-model",
+}
+
+func NewConfigCmd() *cobra.Command {
+	cmd := &cobra.Command{
+		Use:     "config",
+		Short:   "Manage configuration",
+		GroupID: "system",
+	}
+
+	cmd.AddCommand(NewConfigSetCmd())
+	cmd.AddCommand(NewConfigGetCmd())
+	cmd.AddCommand(NewConfigUnsetCmd())
+	cmd.AddCommand(NewConfigDescribeCmd())
+	cmd.AddCommand(NewConfigListCmd())
+
+	return cmd
+}

frontend/cli/cmd/config_describe.go

@@ -0,0 +1,53 @@
+package cmd
+
+import (
+	"fmt"
+
+	"github.com/spf13/cobra"
+)
+
+type configDescription struct {
+	Type        string
+	Description string
+	Example     string
+	Default     string
+}
+
+var configDescriptions = map[string]configDescription{
+	"defaults.agent": {
+		Type:        "String (Agent Name or ID)",
+		Description: "Specifies the default agent to use when running `construct new` without the\n  --agent flag. This allows you to set a preferred agent for new conversations.",
+		Example:     "construct config set defaults.agent \"my-favorite-coder\"",
+	},
+}
+
+func NewConfigDescribeCmd() *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "describe <key>",
+		Short: "Describe a configuration value",
+		Long:  `The "describe" command allows you to describe a configuration value`,
+		Args:  cobra.ExactArgs(1),
+		RunE: func(cmd *cobra.Command, args []string) error {
+			key := args[0]
+			description, ok := configDescriptions[key]
+			if !ok {
+				return fmt.Errorf("unknown configuration key: %s", key)
+			}
+
+			defaultValue := description.Default
+			if defaultValue == "" {
+				defaultValue = "(none)"
+			}
+
+			fmt.Printf("%s\n\n", key)
+			fmt.Printf("  %s\n\n", description.Description)
+			fmt.Printf("  Type                         Default\n")
+			fmt.Printf("  %-28s %s\n\n", description.Type, defaultValue)
+			fmt.Printf("  Example: %s\n", description.Example)
+
+			return nil
+		},
+	}
+
+	return cmd
+}

frontend/cli/cmd/config_get.go

@@ -0,0 +1,23 @@
+package cmd
+
+import "github.com/spf13/cobra"
+
+func NewConfigGetCmd() *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "get <key>",
+		Short: "Get a configuration value",
+		Long:  `The "get" command allows you to get a configuration value`,
+		ValidArgsFunction: func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
+			if len(args) == 0 {
+				return configOptions, cobra.ShellCompDirectiveNoFileComp
+			}
+
+			return []string{}, cobra.ShellCompDirectiveDefault
+		},
+		RunE: func(cmd *cobra.Command, args []string) error {
+			return nil
+		},
+	}
+
+	return cmd
+}

frontend/cli/cmd/config_list.go

@@ -0,0 +1,16 @@
+package cmd
+
+import "github.com/spf13/cobra"
+
+func NewConfigListCmd() *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "list",
+		Short: "List all configuration values",
+		Long:  `The "list" command allows you to list all configuration values`,
+		RunE: func(cmd *cobra.Command, args []string) error {
+			return nil
+		},
+	}
+
+	return cmd
+}

frontend/cli/cmd/config_set.go

@@ -0,0 +1,23 @@
+package cmd
+
+import "github.com/spf13/cobra"
+
+func NewConfigSetCmd() *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "set <key> <value>",
+		Short: "Set a configuration value",
+		Long:  `The "config set" command allows you to set a configuration value`,
+		ValidArgsFunction: func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
+			if len(args) == 0 {
+				return configOptions, cobra.ShellCompDirectiveNoFileComp
+			}
+
+			return []string{}, cobra.ShellCompDirectiveDefault
+		},
+		RunE: func(cmd *cobra.Command, args []string) error {
+			return nil
+		},
+	}
+
+	return cmd
+}

frontend/cli/cmd/config_unset.go

@@ -0,0 +1,23 @@
+package cmd
+
+import "github.com/spf13/cobra"
+
+func NewConfigUnsetCmd() *cobra.Command {
+	cmd := &cobra.Command{
+		Use:   "unset <key>",
+		Short: "Unset a configuration value",
+		Long:  `The "unset" command allows you to unset a configuration value`,
+		ValidArgsFunction: func(cmd *cobra.Command, args []string, toComplete string) ([]string, cobra.ShellCompDirective) {
+			if len(args) == 0 {
+				return configOptions, cobra.ShellCompDirectiveNoFileComp
+			}
+
+			return []string{}, cobra.ShellCompDirectiveDefault
+		},
+		RunE: func(cmd *cobra.Command, args []string) error {
+			return nil
+		},
+	}
+
+	return cmd
+}