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/protocol/src/protocol.rs

@@ -2190,8 +2190,9 @@ pub struct UserMessageEvent {
     #[serde(default, skip_serializing_if = "Vec::is_empty")]
     pub image_details: Vec<Option<ImageDetail>>,
     /// Local file paths sourced from `UserInput::LocalImage`. These are kept so
-    /// the UI can reattach images when editing history, and should not be sent
-    /// to the model or treated as API-ready URLs.
+    /// the UI can reattach images when editing history. Local image prompts may
+    /// include a display form of the path, but these should not be treated as
+    /// API-ready URLs.
     #[serde(default)]
     pub local_images: Vec<std::path::PathBuf>,
     /// Detail hints for `local_images`, indexed in parallel. Missing entries