feat(session): export PrependHistory for shared use across skills

internal/session/history.go

@@ -36,3 +36,21 @@ func FormatHistory(entries []Entry, excludePhase string) string {
 	}
 	return b.String()
 }
+
+// PrependHistory reads the session log for sessionID and prepends a formatted
+// history block to task. Returns task unchanged if sessionID or sessionsDir is
+// empty, or if no prior entries exist.
+func PrependHistory(sessionsDir, sessionID, currentPhase, task string) string {
+	if sessionID == "" || sessionsDir == "" {
+		return task
+	}
+	entries, err := Read(sessionsDir, sessionID)
+	if err != nil || len(entries) == 0 {
+		return task
+	}
+	history := FormatHistory(entries, currentPhase)
+	if history == "" {
+		return task
+	}
+	return history + "\n---\n\n" + task
+}