Add under-development original-resolution view_image support (#13050)

## Summary

Add original-resolution support for `view_image` behind the
under-development `view_image_original_resolution` feature flag.

When the flag is enabled and the target model is `gpt-5.3-codex` or
newer, `view_image` now preserves original PNG/JPEG/WebP bytes and sends
`detail: "original"` to the Responses API instead of using the legacy
resize/compress path.

## What changed

- Added `view_image_original_resolution` as an under-development feature
flag.
- Added `ImageDetail` to the protocol models and support for serializing
`detail: "original"` on tool-returned images.
- Added `PromptImageMode::Original` to `codex-utils-image`.
  - Preserves original PNG/JPEG/WebP bytes.
  - Keeps legacy behavior for the resize path.
- Updated `view_image` to:
- use the shared `local_image_content_items_with_label_number(...)`
helper in both code paths
  - select original-resolution mode only when:
    - the feature flag is enabled, and
    - the model slug parses as `gpt-5.3-codex` or newer
- Kept local user image attachments on the existing resize path; this
change is specific to `view_image`.
- Updated history/image accounting so only `detail: "original"` images
use the docs-based GPT-5 image cost calculation; legacy images still use
the old fixed estimate.
- Added JS REPL guidance, gated on the same feature flag, to prefer JPEG
at 85% quality unless lossless is required, while still allowing other
formats when explicitly requested.
- Updated tests and helper code that construct
`FunctionCallOutputContentItem::InputImage` to carry the new `detail`
field.

## Behavior

### Feature off
- `view_image` keeps the existing resize/re-encode behavior.
- History estimation keeps the existing fixed-cost heuristic.

### Feature on + `gpt-5.3-codex+`
- `view_image` sends original-resolution images with `detail:
"original"`.
- PNG/JPEG/WebP source bytes are preserved when possible.
- History estimation uses the GPT-5 docs-based image-cost calculation
for those `detail: "original"` images.


#### [git stack](https://github.com/magus/git-stack-cli)
- 👉 `1` https://github.com/openai/codex/pull/13050
- ⏳ `2` https://github.com/openai/codex/pull/13331
- ⏳ `3` https://github.com/openai/codex/pull/13049

codex-rs/app-server-protocol/schema/json/EventMsg.json

@@ -3478,6 +3478,16 @@
         },
         {
           "properties": {
+            "detail": {
+              "anyOf": [
+                {
+                  "$ref": "#/definitions/ImageDetail"
+                },
+                {
+                  "type": "null"
+                }
+              ]
+            },
             "image_url": {
               "type": "string"
             },
@@ -3569,6 +3579,15 @@
       ],
       "type": "object"
     },
+    "ImageDetail": {
+      "enum": [
+        "auto",
+        "low",
+        "high",
+        "original"
+      ],
+      "type": "string"
+    },
     "LocalShellAction": {
       "oneOf": [
         {