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/exec/src/lib.rs

@@ -360,6 +360,7 @@ pub async fn run_main(cli: Cli, codex_linux_sandbox_exe: Option<PathBuf>) -> any
                 .collect();
             items.push(UserInput::Text {
                 text: prompt_text.clone(),
+                // CLI input doesn't track UI element ranges, so none are available here.
                 text_elements: Vec::new(),
             });
             let output_schema = load_output_schema(output_schema_path.clone());
@@ -379,6 +380,7 @@ pub async fn run_main(cli: Cli, codex_linux_sandbox_exe: Option<PathBuf>) -> any
                 .collect();
             items.push(UserInput::Text {
                 text: prompt_text.clone(),
+                // CLI input doesn't track UI element ranges, so none are available here.
                 text_elements: Vec::new(),
             });
             let output_schema = load_output_schema(output_schema_path);