fix(proxy): extend image rectifier to Codex /responses text-only path

Codex /responses requests routed to text-only OpenAI-chat upstreams
(e.g. DeepSeek deepseek-v4-flash) failed with HTTP 400 "unknown variant
image_url" when images were sent: the responses->chat conversion turns
input_image items into image_url blocks the model rejects. The media
rectifier previously covered only the Claude adapter, so neither the
proactive strip nor the reactive retry fired for Codex.

- media_retry_should_trigger: accept "Codex" adapter, not just "Claude"
- contains_image_blocks / replace_images: also scan responses `input`
  (input_image) in addition to chat `messages`
- is_image_block_type: match image | image_url | input_image
- is_unsupported_image_error: add "unknown variant" hint for the
  deserialize error
- forward(): proactively run apply_media_prevention for Codex after the
  responses->chat conversion

Proactively strips images for known text-only models (heuristic on by
default) and reactively retries with images replaced on upstream
image-unsupported errors. Adds tests for chat image_url, codex
input_image, the reactive trigger, and the deserialize error match.

src-tauri/src/proxy/forwarder.rs

@@ -159,7 +159,7 @@ impl RequestForwarder {
         provider_body: &Value,
         error: &ProxyError,
     ) -> bool {
-        adapter_name == "Claude"
+        matches!(adapter_name, "Claude" | "Codex")
             && self.rectifier_config.enabled
             && self.rectifier_config.request_media_fallback
             && !already_retried
@@ -1321,7 +1321,7 @@ impl RequestForwarder {
         };
 
         // 转换请求体（如果需要）
-        let request_body = if codex_responses_to_chat {
+        let mut request_body = if codex_responses_to_chat {
             let mut mapped_body = mapped_body;
             let restored = self
                 .codex_chat_history
@@ -1359,6 +1359,10 @@ impl RequestForwarder {
             mapped_body
         };
 
+        if matches!(app_type, AppType::Codex) {
+            self.apply_media_prevention(&mut request_body, provider);
+        }
+
         // 过滤私有参数（以 `_` 开头的字段），防止内部信息泄露到上游
         // 默认使用空白名单，过滤所有 _ 前缀字段
         let filtered_body = prepare_upstream_request_body(request_body);
@@ -3298,6 +3302,18 @@ mod tests {
         })
     }
 
+    fn body_with_codex_input_image(model: &str) -> Value {
+        json!({
+            "model": model,
+            "input": [{
+                "role": "user",
+                "content": [
+                    { "type": "input_image", "image_url": "data:image/png;base64,abc" }
+                ]
+            }]
+        })
+    }
+
     fn image_unsupported_error() -> ProxyError {
         ProxyError::UpstreamError {
             status: 400,
@@ -3385,6 +3401,21 @@ mod tests {
         assert!(fwd.media_retry_should_trigger("Claude", false, &body, &image_unsupported_error()));
     }
 
+    #[test]
+    fn reactive_triggers_for_codex_image_url_deserialize_errors() {
+        let fwd = forwarder_with_rectifier(RectifierConfig::default());
+        let body = body_with_codex_input_image("deepseek-v4-flash");
+        let error = ProxyError::UpstreamError {
+            status: 400,
+            body: Some(
+                r#"{"error":{"message":"Failed to deserialize the JSON body into the target type: messages[11]: unknown variant image_url, expected text"}}"#
+                    .to_string(),
+            ),
+        };
+
+        assert!(fwd.media_retry_should_trigger("Codex", false, &body, &error));
+    }
+
     #[test]
     fn reactive_skipped_when_media_fallback_off() {
         // 关闭 request_media_fallback：上游报图片错误也不触发兜底重试。