fix: drop unsigned gemini tool calls from history

src/agents/pi-embedded-helpers.downgradegeminihistory.test.ts

@@ -0,0 +1,71 @@
+import { describe, expect, it } from "vitest";
+import { downgradeGeminiHistory } from "./pi-embedded-helpers.js";
+
+describe("downgradeGeminiHistory", () => {
+  it("drops unsigned tool calls and matching tool results", () => {
+    const input = [
+      {
+        role: "assistant",
+        content: [
+          { type: "text", text: "hello" },
+          { type: "toolCall", id: "call_1", name: "read", arguments: { path: "/tmp" } },
+        ],
+      },
+      {
+        role: "toolResult",
+        toolCallId: "call_1",
+        content: [{ type: "text", text: "ok" }],
+      },
+      { role: "user", content: "next" },
+    ];
+
+    expect(downgradeGeminiHistory(input)).toEqual([
+      {
+        role: "assistant",
+        content: [{ type: "text", text: "hello" }],
+      },
+      { role: "user", content: "next" },
+    ]);
+  });
+
+  it("keeps signed tool calls and results", () => {
+    const input = [
+      {
+        role: "assistant",
+        content: [
+          {
+            type: "toolCall",
+            id: "call_2",
+            name: "read",
+            arguments: { path: "/tmp" },
+            thought_signature: "sig_123",
+          },
+        ],
+      },
+      {
+        role: "toolResult",
+        toolCallId: "call_2",
+        content: [{ type: "text", text: "ok" }],
+      },
+    ];
+
+    expect(downgradeGeminiHistory(input)).toEqual(input);
+  });
+
+  it("drops assistant messages that only contain unsigned tool calls", () => {
+    const input = [
+      {
+        role: "assistant",
+        content: [{ type: "toolCall", id: "call_3", name: "read", arguments: {} }],
+      },
+      {
+        role: "toolResult",
+        toolCallId: "call_3",
+        content: [{ type: "text", text: "ok" }],
+      },
+      { role: "user", content: "after" },
+    ];
+
+    expect(downgradeGeminiHistory(input)).toEqual([{ role: "user", content: "after" }]);
+  });
+});