Add text element metadata to types (#9235)

Initial type tweaking PR to make the diff of
https://github.com/openai/codex/pull/9116 smaller

This should not change any behavior, just adds some fields to types

codex-rs/protocol/src/user_input.rs

@@ -10,17 +10,19 @@ use ts_rs::TS;
 pub enum UserInput {
     Text {
         text: String,
+        /// UI-defined spans within `text` that should be treated as special elements.
+        /// These are byte ranges into the UTF-8 `text` buffer and are used to render
+        /// or persist rich input markers (e.g., image placeholders) across history
+        /// and resume without mutating the literal text.
+        #[serde(default)]
+        text_elements: Vec<TextElement>,
     },
     /// Pre‑encoded data: URI image.
-    Image {
-        image_url: String,
-    },
+    Image { image_url: String },
 
     /// Local image path provided by the user.  This will be converted to an
     /// `Image` variant (base64 data URL) during request serialization.
-    LocalImage {
-        path: std::path::PathBuf,
-    },
+    LocalImage { path: std::path::PathBuf },
 
     /// Skill selected by the user (name + path to SKILL.md).
     Skill {
@@ -28,3 +30,28 @@ pub enum UserInput {
         path: std::path::PathBuf,
     },
 }
+
+#[derive(Debug, Clone, Deserialize, Serialize, PartialEq, TS, JsonSchema)]
+pub struct TextElement {
+    /// Byte range in the parent `text` buffer that this element occupies.
+    pub byte_range: ByteRange,
+    /// Optional human-readable placeholder for the element, displayed in the UI.
+    pub placeholder: Option<String>,
+}
+
+#[derive(Debug, Clone, Copy, Deserialize, Serialize, PartialEq, Eq, TS, JsonSchema)]
+pub struct ByteRange {
+    /// Start byte offset (inclusive) within the UTF-8 text buffer.
+    pub start: usize,
+    /// End byte offset (exclusive) within the UTF-8 text buffer.
+    pub end: usize,
+}
+
+impl From<std::ops::Range<usize>> for ByteRange {
+    fn from(range: std::ops::Range<usize>) -> Self {
+        Self {
+            start: range.start,
+            end: range.end,
+        }
+    }
+}