refactor(open-sse): add reasoningDelta helper, dedup thinking deltas (B4)

Centralize the reasoning_content delta shape (optional assistant role) used by
claude/gemini/kiro/codex/commandcode response translators. Keeps the cross-format
convention consistent for future translators. Output byte-for-byte identical;
golden + gate clean. Ollama left as-is (mutates existing delta object).

Co-authored-by: Cursor <cursoragent@cursor.com>

open-sse/translator/response/commandcode-to-openai.js

@@ -18,6 +18,7 @@
 import { register } from "../index.js";
 import { FORMATS } from "../formats.js";
 import { buildChunk } from "../helpers/chunkBuilder.js";
+import { reasoningDelta } from "../helpers/reasoningHelper.js";
 
 function ensureState(state, model) {
   if (!state.responseId) {
@@ -96,9 +97,7 @@ export function convertCommandCodeToOpenAI(chunk, state) {
       const text = event.text || "";
       if (!text) break;
       // Map reasoning to OpenAI "reasoning_content" field (used by deepseek-reasoner-style clients).
-      const delta = state.chunkIndex === 0
-        ? { role: "assistant", reasoning_content: text }
-        : { reasoning_content: text };
+      const delta = reasoningDelta(text, state.chunkIndex === 0);
       state.chunkIndex++;
       out.push(makeChunk(state, delta));
       break;