Add config loading primitives

internal/core/config/redaction.go

@@ -0,0 +1,14 @@
+package config
+
+const redactedSecret = "[REDACTED]"
+
+func (c Config) Redacted() Config {
+	redacted := cloneConfig(c)
+	for id, profile := range redacted.LLMProfiles {
+		if profile.APIKey != "" {
+			profile.APIKey = redactedSecret
+		}
+		redacted.LLMProfiles[id] = profile
+	}
+	return redacted
+}