Make text field optional in file annotation content schema

The file-parser plugin returns content arrays containing both text
and image elements. Image elements (type: "image_url") do not have
a text property, causing validation errors.

This change makes the text field optional to support both element
types whilst maintaining backwards compatibility with text-only
content.

Fixes validation error: "Invalid input: expected string, received undefined"

Signed-off-by: Sora Morimoto <sora@morimoto.io>

Author: smorimoto

src/chat/schemas.ts

@@ -113,7 +113,7 @@ export const OpenRouterNonStreamChatCompletionResponseSchema = z.union([
                                 z
                                   .object({
                                     type: z.string(),
-                                    text: z.string(),
+                                    text: z.string().optional(),
                                   })
                                   .passthrough(),
                               )
@@ -237,7 +237,7 @@ export const OpenRouterStreamChatCompletionChunkSchema = z.union([
                                 z
                                   .object({
                                     type: z.string(),
-                                    text: z.string(),
+                                    text: z.string().optional(),
                                   })
                                   .passthrough(),
                               )