fix: sanitize thinking blocks for GitHub Copilot Claude models (openclaw#19459) thanks @jackheuberger

Verified:
- pnpm build
- pnpm check
- pnpm test:macmini

Co-authored-by: jackheuberger <12731288+jackheuberger@users.noreply.github.com>
Co-authored-by: Tak Hoffman <781889+Takhoffman@users.noreply.github.com>

src/agents/pi-embedded-runner/thinking.ts

@@ -0,0 +1,47 @@
+import type { AgentMessage } from "@mariozechner/pi-agent-core";
+
+type AssistantContentBlock = Extract<AgentMessage, { role: "assistant" }>["content"][number];
+
+/**
+ * Strip all `type: "thinking"` content blocks from assistant messages.
+ *
+ * If an assistant message becomes empty after stripping, it is replaced with
+ * a synthetic `{ type: "text", text: "" }` block to preserve turn structure
+ * (some providers require strict user/assistant alternation).
+ *
+ * Returns the original array reference when nothing was changed (callers can
+ * use reference equality to skip downstream work).
+ */
+export function dropThinkingBlocks(messages: AgentMessage[]): AgentMessage[] {
+  let touched = false;
+  const out: AgentMessage[] = [];
+  for (const msg of messages) {
+    if (!msg || typeof msg !== "object" || msg.role !== "assistant") {
+      out.push(msg);
+      continue;
+    }
+    if (!Array.isArray(msg.content)) {
+      out.push(msg);
+      continue;
+    }
+    const nextContent: AssistantContentBlock[] = [];
+    let changed = false;
+    for (const block of msg.content) {
+      if (block && typeof block === "object" && (block as { type?: unknown }).type === "thinking") {
+        touched = true;
+        changed = true;
+        continue;
+      }
+      nextContent.push(block);
+    }
+    if (!changed) {
+      out.push(msg);
+      continue;
+    }
+    // Preserve the assistant turn even if all blocks were thinking-only.
+    const content =
+      nextContent.length > 0 ? nextContent : [{ type: "text", text: "" } as AssistantContentBlock];
+    out.push({ ...msg, content });
+  }
+  return touched ? out : messages;
+}