## Summary

Brief description of what this PR does and why.

## Changes

-
-

## Test Plan

Describe how you tested this change.

- [ ] Existing tests pass (`cargo test --workspace`)
- [ ] New tests added where appropriate
- [ ] Manually tested on macOS / Linux (specify which)
- [ ] If a Mermaid block changed, verified rendering in TUI and via `mermaid-text` CLI

## Checklist

- [ ] CHANGELOG.md entry added (root for `markdown-tui-explorer`, crate-local for `mermaid-text`)
- [ ] No new `clippy` warnings (`cargo clippy --all-targets -- -D warnings`)
- [ ] Documentation updated if public API changed
- [ ] Version bumped in `Cargo.toml` if user-visible

## Linked Issue

Closes #
