fix: add null/non-object guards to textPartCount filter in empty output error path

The filter callback for textPartCount directly accessed part.type and
part.text without checking if part is a valid object first. If
responseParts contains null/undefined entries, getOpenCodeTextResponse
safely skips them (returning empty string), triggering the empty-output
branch, but the unguarded filter would throw a TypeError before the
error could be properly tagged and handled.

Add the same guards used in getOpenCodeTextResponse: check for truthy,
object type, and property existence before accessing values.

Author: cursoragent

apps/server/src/textGeneration/OpenCodeTextGeneration.ts

@@ -442,7 +442,13 @@ export const makeOpenCodeTextGeneration = Effect.fn("makeOpenCodeTextGeneration"
             ...promptContext,
             responsePartCount: responseParts.length,
             textPartCount: responseParts.filter(
-              (part) => part.type === "text" && typeof part.text === "string",
+              (part) =>
+                !!part &&
+                typeof part === "object" &&
+                "type" in part &&
+                part.type === "text" &&
+                "text" in part &&
+                typeof part.text === "string",
             ).length,
           });
         }