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/mcp-server/src/codex_tool_runner.rs

@@ -122,6 +122,7 @@ pub async fn run_codex_tool_session(
         op: Op::UserInput {
             items: vec![UserInput::Text {
                 text: initial_prompt.clone(),
+                // MCP tool prompts are plain text with no UI element ranges.
                 text_elements: Vec::new(),
             }],
             final_output_json_schema: None,
@@ -167,7 +168,7 @@ pub async fn run_codex_tool_session_reply(
         .submit(Op::UserInput {
             items: vec![UserInput::Text {
                 text: prompt,
-                // Plain text conversion has no UI element ranges.
+                // MCP tool prompts are plain text with no UI element ranges.
                 text_elements: Vec::new(),
             }],
             final_output_json_schema: None,