[TUI] Rich Markdown mode still renders source heading and list markers

What issue are you seeing?

With tui.raw_output_mode set to false, Codex correctly selects the rich transcript renderer, but the rendered output still resembles raw Markdown:

• headings re-insert their source # markers
• unordered lists render with the source - marker

For example, rich mode currently displays output shaped like:

## Summary
- first item

This makes the rich/raw setting appear ineffective for headings and lists even though the mode switch itself is working.

Expected behavior

Rich mode should communicate Markdown structure through terminal styling and semantic bullets:

Summary
• first item

Raw mode should continue preserving the original Markdown source:

## Summary
- first item

Ordered lists should keep their semantic numbering in rich mode.

Root cause

In codex-rs/tui/src/markdown_render.rs, start_heading explicitly inserts a span containing the repeated # marker. The unordered-list branch similarly inserts - as the displayed marker. These are renderer decisions rather than a configuration or integration issue.

Prepared patch

I prepared and fully tested a patch and would like to contribute it, but this repository currently restricts pull-request creation to collaborators and the contributing guide says external PRs are not accepted. I am opening this issue so the maintainers can evaluate or port the change.

• Commit: https://github.com/youngjunning/codex/commit/ca9963182e5f34e7e4036e4e11e8fb3f451b9b0b
• Compare: https://github.com/openai/codex/compare/main...youngjunning:codex:fix/tui-rich-markdown-markers

The patch:

• removes source # markers from rich heading rendering
• uses • for unordered lists
• preserves ordered numbering
• keeps raw mode unchanged
• updates renderer, streaming, wrapping, and snapshot coverage

Validation

• RUST_MIN_STACK=16777216 cargo test -p codex-tui -- --test-threads=1
  • 3793 library tests passed, 2 ignored
  • 10 integration tests passed, 4 ignored
  • manager dependency regression test passed
• cargo fmt --all -- --check
• git diff --check

The raw/rich snapshot coverage explicitly verifies that raw output retains ## and -, while rich output renders the heading without # and the unordered item with •.

Start in codex-rs/tui/src/markdown_render.rs, especially the heading and unordered-list rendering paths described in the issue. Run RUST_MIN_STACK=16777216 cargo test -p codex-tui -- --test-threads=1 and review the raw/rich snapshot coverage. Done means rich headings omit source # markers, unordered lists use •, ordered lists retain numbering, and raw mode remains unchanged.