Persist text elements through TUI input and history (#9393)

Continuation of breaking up this PR
https://github.com/openai/codex/pull/9116

## Summary
- Thread user text element ranges through TUI/TUI2 input, submission,
queueing, and history so placeholders survive resume/edit flows.
- Preserve local image attachments alongside text elements and rehydrate
placeholders when restoring drafts.
- Keep model-facing content shapes clean by attaching UI metadata only
to user input/events (no API content changes).

## Key Changes
- TUI/TUI2 composer now captures text element ranges, trims them with
text edits, and restores them when submission is suppressed.
- User history cells render styled spans for text elements and keep
local image paths for future rehydration.
- Initial chat widget bootstraps accept empty `initial_text_elements` to
keep initialization uniform.
- Protocol/core helpers updated to tolerate the new InputText field
shape without changing payloads sent to the API.

codex-rs/tui/src/public_widgets/composer_input.rs

@@ -48,13 +48,14 @@ impl ComposerInput {
 
     /// Clear the input text.
     pub fn clear(&mut self) {
-        self.inner.set_text_content(String::new());
+        self.inner
+            .set_text_content(String::new(), Vec::new(), Vec::new());
     }
 
     /// Feed a key event into the composer and return a high-level action.
     pub fn input(&mut self, key: KeyEvent) -> ComposerAction {
         let action = match self.inner.handle_key_event(key).0 {
-            InputResult::Submitted(text) => ComposerAction::Submitted(text),
+            InputResult::Submitted { text, .. } => ComposerAction::Submitted(text),
             _ => ComposerAction::None,
         };
         self.drain_app_events();