fix: add store:false to Chat Completions and /responses fallback (#578)

Set store: false in the request body for both the Chat Completions path
and the /responses fallback path in openaiShim.ts.

The codexShim (Responses API primary path) already sets store: false.
The Chat Completions path and the /responses fallback in openaiShim were
missing it.

store: false tells the API provider not to persist conversation data for
model training, logging, or other non-operational purposes. This is a
privacy measure — it does not affect caching or functionality.

Note: Whether third-party proxies (e.g. GitHub Copilot) honour this
parameter is provider-dependent, but setting it is a reasonable default
for user privacy.

Co-authored-by: Zartris <14197299+Zartris@users.noreply.github.com>

src/services/api/openaiShim.ts

@@ -1184,6 +1184,7 @@ class OpenAIShimMessages {
       model: request.resolvedModel,
       messages: openaiMessages,
       stream: params.stream ?? false,
+      store: false,
     }
     // Convert max_tokens to max_completion_tokens for OpenAI API compatibility.
     // Azure OpenAI requires max_completion_tokens and does not accept max_tokens.
@@ -1358,6 +1359,7 @@ class OpenAIShimMessages {
               }>,
             ),
             stream: params.stream ?? false,
+            store: false,
           }
 
           if (!Array.isArray(responsesBody.input) || responsesBody.input.length === 0) {