Expose local image paths to models (#25944)

## Why

Local image attachments include image bytes, but the adjacent
model-visible label omits the source path. Exposing the path lets
model-selected workflows refer back to the intended local image
explicitly.

## What changed

- Include an escaped `path` attribute in model-visible local image
opening tags.
- Reuse the path-aware marker generator in rollout coverage.
- Update protocol, replay, and rollout coverage for the new request
shape.

## Validation

- `just fmt`
- `just test -p codex-protocol`
- `just test -p codex-core skips_local_image_label_text`
- `just test -p codex-core
copy_paste_local_image_persists_rollout_request_shape`
- `git diff --check`

codex-rs/core/src/event_mapping_tests.rs

@@ -67,7 +67,7 @@ fn parses_user_message_with_text_and_two_images() {
 #[test]
 fn skips_local_image_label_text() {
     let image_url = "data:image/png;base64,abc".to_string();
-    let label = codex_protocol::models::local_image_open_tag_text(/*label_number*/ 1);
+    let label = r#"<image name=[Image #1] path="/tmp/local.png">"#.to_string();
     let user_text = "Please review this image.".to_string();
 
     let item = ResponseItem::Message {