core: resize all history images behind a feature flag (#27247)

## Summary

Adds complete client-side image preparation behind the default-off
`resize_all_images` feature flag.

When enabled, local image producers defer decoding and resizing. Images
are prepared centrally before insertion into conversation history,
covering user input, `view_image`, and structured tool-output images.

## Behavior

- Processes base64 `data:` images in messages and function/custom tool
outputs.
- Leaves non-data URLs, including HTTP(S) URLs, unchanged.
- Applies image-detail budgets:
  - `high` and omitted: 2048px maximum dimension and 2.5K 32px patches.
  - `original`: 6000px maximum dimension and 10K 32px patches.
  - `auto`: uses the same 2048px / 2.5K-patch budget as high.
  - `low`: unsupported and replaced with an actionable placeholder.
- Preserves original image bytes when no resize or format conversion is
needed.
- Enforces the shared 1 GiB encoded and decoded data-URL sanity limits.
- Replaces only an image that fails preparation, preserving sibling
content and tool-output metadata.
- Uses bounded placeholders distinguishing generic processing failures,
oversized images, and unsupported `low` detail.
- Prepares resumed and forked history before installing it as live
history without modifying persisted rollouts.

## Flag-Off Behavior

When `resize_all_images` is disabled:

- Existing local user-input and `view_image` processing remains
unchanged.
- Existing decoding and error behavior remains unchanged.
- Arbitrary tool-output images are not processed.
- HTTP(S) image URLs continue to be forwarded unchanged.


#### [git stack](https://github.com/magus/git-stack-cli)
- ✅ `1` https://github.com/openai/codex/pull/27245
- 👉 `2` https://github.com/openai/codex/pull/27247
- ⏳ `3` https://github.com/openai/codex/pull/27246
- ⏳ `4` https://github.com/openai/codex/pull/27266

codex-rs/core/src/tools/handlers/view_image.rs

@@ -1,3 +1,4 @@
+use codex_features::Feature;
 use codex_protocol::items::ImageViewItem;
 use codex_protocol::items::TurnItem;
 use codex_protocol::models::DEFAULT_IMAGE_DETAIL;
@@ -8,6 +9,7 @@ use codex_protocol::models::ImageDetail;
 use codex_protocol::models::ResponseInputItem;
 use codex_protocol::openai_models::InputModality;
 use codex_utils_image::PromptImageMode;
+use codex_utils_image::data_url_from_bytes;
 use codex_utils_image::load_for_prompt_bytes;
 use serde::Deserialize;
 
@@ -175,25 +177,30 @@ impl ViewImageHandler {
         let can_request_original_detail = can_request_original_image_detail(&turn.model_info);
         let use_original_detail =
             can_request_original_detail && matches!(detail, Some(ViewImageDetail::Original));
-        let image_mode = if use_original_detail {
-            PromptImageMode::Original
-        } else {
-            PromptImageMode::ResizeToFit
-        };
         let image_detail = if use_original_detail {
             ImageDetail::Original
         } else {
             DEFAULT_IMAGE_DETAIL
         };
 
-        let image =
-            load_for_prompt_bytes(abs_path.as_path(), file_bytes, image_mode).map_err(|error| {
-                FunctionCallError::RespondToModel(format!(
-                    "unable to process image at `{}`: {error}",
-                    abs_path.display()
-                ))
-            })?;
-        let image_url = image.into_data_url();
+        let image_url = if turn.features.enabled(Feature::ResizeAllImages) {
+            // The history insertion path owns image decoding and resizing when this is enabled.
+            data_url_from_bytes("application/octet-stream", &file_bytes)
+        } else {
+            let image_mode = if use_original_detail {
+                PromptImageMode::Original
+            } else {
+                PromptImageMode::ResizeToFit
+            };
+            load_for_prompt_bytes(abs_path.as_path(), file_bytes, image_mode)
+                .map_err(|error| {
+                    FunctionCallError::RespondToModel(format!(
+                        "unable to process image at `{}`: {error}",
+                        abs_path.display()
+                    ))
+                })?
+                .into_data_url()
+        };
 
         let item = TurnItem::ImageView(ImageViewItem {
             id: call_id,
@@ -218,7 +225,7 @@ pub struct ViewImageOutput {
 
 impl ToolOutput for ViewImageOutput {
     fn log_preview(&self) -> String {
-        self.image_url.clone()
+        format!("<image data URL omitted: {} bytes>", self.image_url.len())
     }
 
     fn success_for_logging(&self) -> bool {
@@ -264,6 +271,16 @@ mod tests {
     use std::sync::Arc;
     use tokio::sync::Mutex;
 
+    #[test]
+    fn log_preview_omits_image_data() {
+        let output = ViewImageOutput {
+            image_url: "data:image/png;base64,AAA".to_string(),
+            image_detail: DEFAULT_IMAGE_DETAIL,
+        };
+
+        assert_eq!(output.log_preview(), "<image data URL omitted: 25 bytes>");
+    }
+
     #[test]
     fn code_mode_result_returns_image_url_object() {
         let output = ViewImageOutput {