feat(migrate): add picoclaw migrate command for OpenClaw workspace migration

Add a new `picoclaw migrate` CLI command that detects an existing OpenClaw
installation and migrates workspace files and configuration to PicoClaw.

Workspace markdown files (SOUL.md, AGENTS.md, USER.md, TOOLS.md, HEARTBEAT.md,
memory/, skills/) are copied 1:1. Config keys are mapped from OpenClaw's
camelCase JSON format to PicoClaw's snake_case format with provider and channel
field mapping.

Supports --dry-run, --refresh, --config-only, --workspace-only, --force flags.
Existing PicoClaw files are never silently overwritten; backups are created.

Closes #27

Co-Authored-By: Claude Opus 4.6 <noreply@anthropic.com>

pkg/migrate/workspace.go

@@ -0,0 +1,106 @@
+package migrate
+
+import (
+	"os"
+	"path/filepath"
+)
+
+var migrateableFiles = []string{
+	"AGENTS.md",
+	"SOUL.md",
+	"USER.md",
+	"TOOLS.md",
+	"HEARTBEAT.md",
+}
+
+var migrateableDirs = []string{
+	"memory",
+	"skills",
+}
+
+func PlanWorkspaceMigration(srcWorkspace, dstWorkspace string, force bool) ([]Action, error) {
+	var actions []Action
+
+	for _, filename := range migrateableFiles {
+		src := filepath.Join(srcWorkspace, filename)
+		dst := filepath.Join(dstWorkspace, filename)
+		action := planFileCopy(src, dst, force)
+		if action.Type != ActionSkip || action.Description != "" {
+			actions = append(actions, action)
+		}
+	}
+
+	for _, dirname := range migrateableDirs {
+		srcDir := filepath.Join(srcWorkspace, dirname)
+		if _, err := os.Stat(srcDir); os.IsNotExist(err) {
+			continue
+		}
+		dirActions, err := planDirCopy(srcDir, filepath.Join(dstWorkspace, dirname), force)
+		if err != nil {
+			return nil, err
+		}
+		actions = append(actions, dirActions...)
+	}
+
+	return actions, nil
+}
+
+func planFileCopy(src, dst string, force bool) Action {
+	if _, err := os.Stat(src); os.IsNotExist(err) {
+		return Action{
+			Type:        ActionSkip,
+			Source:      src,
+			Destination: dst,
+			Description: "source file not found",
+		}
+	}
+
+	_, dstExists := os.Stat(dst)
+	if dstExists == nil && !force {
+		return Action{
+			Type:        ActionBackup,
+			Source:      src,
+			Destination: dst,
+			Description: "destination exists, will backup and overwrite",
+		}
+	}
+
+	return Action{
+		Type:        ActionCopy,
+		Source:      src,
+		Destination: dst,
+		Description: "copy file",
+	}
+}
+
+func planDirCopy(srcDir, dstDir string, force bool) ([]Action, error) {
+	var actions []Action
+
+	err := filepath.Walk(srcDir, func(path string, info os.FileInfo, err error) error {
+		if err != nil {
+			return err
+		}
+
+		relPath, err := filepath.Rel(srcDir, path)
+		if err != nil {
+			return err
+		}
+
+		dst := filepath.Join(dstDir, relPath)
+
+		if info.IsDir() {
+			actions = append(actions, Action{
+				Type:        ActionCreateDir,
+				Destination: dst,
+				Description: "create directory",
+			})
+			return nil
+		}
+
+		action := planFileCopy(path, dst, force)
+		actions = append(actions, action)
+		return nil
+	})
+
+	return actions, err
+}