fix: hide message_id hints in web chat

src/gateway/chat-sanitize.test.ts

@@ -0,0 +1,42 @@
+import { describe, expect, test } from "vitest";
+import { stripEnvelopeFromMessage } from "./chat-sanitize.js";
+
+describe("stripEnvelopeFromMessage", () => {
+  test("removes message_id hint lines from user messages", () => {
+    const input = {
+      role: "user",
+      content: "[WhatsApp 2026-01-24 13:36] yolo\n[message_id: 7b8b]",
+    };
+    const result = stripEnvelopeFromMessage(input) as { content?: string };
+    expect(result.content).toBe("yolo");
+  });
+
+  test("removes message_id hint lines from text content arrays", () => {
+    const input = {
+      role: "user",
+      content: [{ type: "text", text: "hi\n[message_id: abc123]" }],
+    };
+    const result = stripEnvelopeFromMessage(input) as {
+      content?: Array<{ type: string; text?: string }>;
+    };
+    expect(result.content?.[0]?.text).toBe("hi");
+  });
+
+  test("does not strip inline message_id text that is part of a line", () => {
+    const input = {
+      role: "user",
+      content: "I typed [message_id: 123] on purpose",
+    };
+    const result = stripEnvelopeFromMessage(input) as { content?: string };
+    expect(result.content).toBe("I typed [message_id: 123] on purpose");
+  });
+
+  test("does not strip assistant messages", () => {
+    const input = {
+      role: "assistant",
+      content: "note\n[message_id: 123]",
+    };
+    const result = stripEnvelopeFromMessage(input) as { content?: string };
+    expect(result.content).toBe("note\n[message_id: 123]");
+  });
+});