Markdown content jumbled up in TUI preview

When we're rendering the Markdown in the TUI as preview, we have a mess...

(test/test_data/real_projects/-Users-dain-workspace-coderabbit-review-helper, session 741790a4-4fe2-4644-9a51-fb4482074060.jsonl)

Rendering that session alone works fine:

uv run claude-code-log test/test_data/real_projects/-Users-dain-workspace-coderabbit-review-helper/741790a4-4fe2-4644-9a51-fb4482074060.jsonl -o 741790a4.md -f md 

We get:

## 🤷 User: *I checked and it looks great!*

```
I checked and it looks great!

Spotted another issue though, we seem to be printing `Lines 0` in each title which doesn't make sense.

It also says **Total files with feedback:** 1 despite later a lot of different files mentioned.

Can you please investigate these issues? I s'pose we should be grouping feedback by file and correctly printing line numbers, and the omitting the Lines: n bit if we can't find line numbers in the feedback
```

### 🤖 Assistant: *I'll investigate these issues - the "Lines…*

<details>
<summary>Thinking...</summary>

> The user has noticed two issues:
> 
> 1. "Lines 0" appearing in titles - doesn't make sense
> 2. "Total files with feedback: 1" but multiple files mentioned - incorrect grouping
> 
> They want me to investigate these issues. They suggest:
> - Group feedback by file
> - Correctly print line numbers
> - Omit "Lines: n" if we can't find line numbers
> 
> Since I'm in plan mode, I need to:
> 1. Use a Task tool with Plan subagent to investigate the issues
> 2. Present a plan using ExitPlanMode
> 
> Let me investigate what's happening with the line numbers and file grouping.
</details>

> I'll investigate these issues - the "Lines 0" problem and the incorrect file grouping.

#### 🤖 Task (Plan): *Investigate line number and file grouping issues*

(same results with --no-cache)

No idea about what's going on, yet.

Start with the TUI preview path and reproduce the issue using test/test_data/real_projects/-Users-dain-workspace-coderabbit-review-helper/741790a4-4fe2-4644-9a51-fb4482074060.jsonl. Compare its output with the standalone uv run claude-code-log ... -o 741790a4.md -f md result, including --no-cache. Done means the TUI preview preserves the Markdown structure and does not show the reported jumbled content.