fix: clean tool schemas and thinking blocks for google-antigravity (openclaw#19732) thanks @Oceanswave

Verified:
- pnpm install --frozen-lockfile
- pnpm build
- pnpm check
- pnpm test:macmini

Co-authored-by: Oceanswave <760674+Oceanswave@users.noreply.github.com>
Co-authored-by: Tak Hoffman <781889+Takhoffman@users.noreply.github.com>

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

@@ -101,6 +101,12 @@ export function sanitizeAntigravityThinkingBlocks(messages: AgentMessage[]): Age
       const candidate =
         rec.thinkingSignature ?? rec.signature ?? rec.thought_signature ?? rec.thoughtSignature;
       if (!isValidAntigravitySignature(candidate)) {
+        // Preserve reasoning content as plain text when signatures are invalid/missing.
+        // Antigravity Claude rejects unsigned thinking blocks, but dropping them loses context.
+        const thinkingText = (block as { thinking?: unknown }).thinking;
+        if (typeof thinkingText === "string" && thinkingText.trim()) {
+          nextContent.push({ type: "text", text: thinkingText } as AssistantContentBlock);
+        }
         contentChanged = true;
         continue;
       }