feat(v0.5.3): ResolveSessionMode env var resolver

internal/config/config.go

@@ -1,6 +1,7 @@
 package config
 
 import (
+	"fmt"
 	"os"
 	"path/filepath"
 	"runtime"
@@ -148,6 +149,25 @@ func defaultSeedDir(leaf string) string {
 	return filepath.Join(home, ".config", "ctask", leaf)
 }
 
+// ResolveSessionMode returns "direct" or "persistent" based on CTASK_SESSION_MODE.
+// Default (unset/empty) is "direct". Any other value falls back to "direct"
+// after printing a stderr warning. Used by entry commands (new, resume, last,
+// open) to dispatch between the standard session.Run path and the tmux-backed
+// persistent path.
+func ResolveSessionMode() string {
+	v := os.Getenv("CTASK_SESSION_MODE")
+	switch v {
+	case "", "direct":
+		return "direct"
+	case "persistent":
+		return "persistent"
+	default:
+		fmt.Fprintf(os.Stderr,
+			"[ctask] warning: CTASK_SESSION_MODE=%q is not recognized; using direct mode\n", v)
+		return "direct"
+	}
+}
+
 // expandPath expands a leading ~/ and resolves to an absolute path when possible.
 func expandPath(p string) string {
 	if strings.HasPrefix(p, "~/") || p == "~" {