fix(gemini): normalize contents and handle intermediate tool responses in Antigravity

Co-Authored-By: Claude Code <noreply@anthropic.com>

open-sse/translator/formats/gemini.js

@@ -432,3 +432,21 @@ export function cleanJSONSchemaForAntigravity(schema) {
   return cleaned;
 }
 
+// Merge adjacent same-role messages, strip empty parts, ensure initial user turn
+export function normalizeGeminiContents(contents) {
+  const out = [];
+  for (const c of contents || []) {
+    if (!c?.role || !Array.isArray(c.parts)) continue;
+    const parts = c.parts.filter(p => p && Object.keys(p).length > 0);
+    if (parts.length === 0) continue;
+    const last = out.at(-1);
+    if (last?.role === c.role) last.parts.push(...parts);
+    else out.push({ ...c, parts: [...parts] });
+  }
+  if (out.length > 0 && out[0].role !== "user") {
+    out.unshift({ role: "user", parts: [{ text: "..." }] });
+  }
+  return out;
+}
+
+