fix(claude): drop server_tool_use blocks carrying a foreign id

Anthropic validates server_tool_use.id against ^srvtoolu_[a-zA-Z0-9_]+$
and 400s the whole request when one does not match. A combo that falls
back to a provider with its own built-in tools (z.ai/glm emits
OpenAI-style call_ ids for analyze_image) leaves such blocks in the
history, so every later Claude turn fails.

Extend normalizeClaudePassthrough to drop those blocks (reusing the
existing loop), drop the paired tool_result / web_search_tool_result
referencing a dropped id, and drop empty text blocks plus messages left
with no content. Well-formed srvtoolu_ blocks and regular tool_use ids
are untouched.

tests/unit/claude-foreign-server-tool-use.test.js

@@ -0,0 +1,88 @@
+// A combo that mixes providers leaks foreign block shapes into the Claude history.
+// Anthropic validates server_tool_use ids against ^srvtoolu_[a-zA-Z0-9_]+$ and 400s
+// the whole request when a provider (e.g. z.ai/glm) emits OpenAI-style call_ ids.
+import { describe, it, expect } from "vitest";
+import { normalizeClaudePassthrough } from "../../open-sse/translator/formats/claude.js";
+
+const glmServerToolUse = () => ({
+  role: "assistant",
+  content: [
+    { type: "text", text: "searching" },
+    { type: "server_tool_use", id: "call_50b82aba1b754d82a4408a53", name: "analyze_image", input: {} },
+  ],
+});
+
+describe("normalizeClaudePassthrough — foreign server_tool_use ids", () => {
+  it("drops a server_tool_use block whose id is not an srvtoolu_ id", () => {
+    const out = normalizeClaudePassthrough({ messages: [glmServerToolUse()] });
+    expect(out.messages[0].content).toEqual([{ type: "text", text: "searching" }]);
+  });
+
+  it("drops the paired tool_result so no orphan reference is left behind", () => {
+    const out = normalizeClaudePassthrough({
+      messages: [
+        glmServerToolUse(),
+        {
+          role: "user",
+          content: [
+            { type: "tool_result", tool_use_id: "call_50b82aba1b754d82a4408a53", content: "boom" },
+            { type: "text", text: "keep me" },
+          ],
+        },
+      ],
+    });
+    expect(out.messages[1].content).toEqual([{ type: "text", text: "keep me" }]);
+  });
+
+  it("keeps a well-formed Anthropic server_tool_use block", () => {
+    const block = { type: "server_tool_use", id: "srvtoolu_01EUi6RNgHntbStfCjgLyLzz", name: "web_search", input: {} };
+    const out = normalizeClaudePassthrough({ messages: [{ role: "assistant", content: [block] }] });
+    expect(out.messages[0].content).toEqual([block]);
+  });
+
+  it("keeps regular tool_use blocks, whatever their id looks like", () => {
+    const block = { type: "tool_use", id: "call_942248714fef4a9abb8e8eff", name: "Bash", input: { command: "ls" } };
+    const out = normalizeClaudePassthrough({ messages: [{ role: "assistant", content: [block] }] });
+    expect(out.messages[0].content).toEqual([block]);
+  });
+
+  it("drops a message whose blocks were all stripped instead of padding it with empty text", () => {
+    const out = normalizeClaudePassthrough({
+      messages: [
+        { role: "user", content: [{ type: "text", text: "hi" }] },
+        { role: "assistant", content: [{ type: "server_tool_use", id: "call_x", name: "analyze_image", input: {} }] },
+        { role: "user", content: [{ type: "text", text: "bye" }] },
+      ],
+    });
+    expect(out.messages).toHaveLength(2);
+    expect(out.messages.map(m => m.role)).toEqual(["user", "user"]);
+  });
+
+  it("strips empty text blocks a client put in the history (Anthropic 400s them)", () => {
+    const out = normalizeClaudePassthrough({
+      messages: [{ role: "assistant", content: [{ type: "text", text: "real" }, { type: "text", text: "" }] }],
+    });
+    expect(out.messages[0].content).toEqual([{ type: "text", text: "real" }]);
+  });
+
+  it("drops a message whose content is a single empty text block", () => {
+    const out = normalizeClaudePassthrough({
+      messages: [
+        { role: "user", content: [{ type: "text", text: "hi" }] },
+        { role: "assistant", content: [{ type: "text", text: "" }] },
+      ],
+    });
+    expect(out.messages).toHaveLength(1);
+  });
+
+  it("drops a message whose string content is empty", () => {
+    const out = normalizeClaudePassthrough({
+      messages: [
+        { role: "user", content: "hello" },
+        { role: "assistant", content: "" },
+      ],
+    });
+    expect(out.messages).toHaveLength(1);
+    expect(out.messages[0].content).toBe("hello");
+  });
+});