fix: normalize heartbeat targets

src/config/zod-schema.agent-runtime.ts

@@ -22,19 +22,7 @@ export const HeartbeatSchema = z
     model: z.string().optional(),
     session: z.string().optional(),
     includeReasoning: z.boolean().optional(),
-    target: z
-      .union([
-        z.literal("last"),
-        z.literal("whatsapp"),
-        z.literal("telegram"),
-        z.literal("discord"),
-        z.literal("slack"),
-        z.literal("msteams"),
-        z.literal("signal"),
-        z.literal("imessage"),
-        z.literal("none"),
-      ])
-      .optional(),
+    target: z.string().optional(),
     to: z.string().optional(),
     prompt: z.string().optional(),
     ackMaxChars: z.number().int().nonnegative().optional(),