revert: remove unnecessary AGENT.md skip in onboard

Reverts 02d0c04 and 74deae1. The test failure was caused by a local
leftover workspace/AGENT.md file (gitignored but embedded by go:embed).
Deleting the local file fixes the root cause; the code-level skip was
never needed.

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

cmd/picoclaw/internal/onboard/helpers.go

@@ -10,9 +10,6 @@ import (
 	"github.com/sipeed/picoclaw/pkg/config"
 )
 
-// legacyAgentFile is the old workspace template filename superseded by AGENTS.md.
-const legacyAgentFile = "AGENT.md"
-
 func onboard() {
 	configPath := internal.GetConfigPath()
 
@@ -73,11 +70,6 @@ func copyEmbeddedToTarget(targetDir string) error {
 			return nil
 		}
 
-		// Skip legacy file superseded by AGENTS.md
-		if filepath.Base(path) == legacyAgentFile {
-			return nil
-		}
-
 		// Read embedded file
 		data, err := embeddedFiles.ReadFile(path)
 		if err != nil {