[BUG] VS Code extension: "Show more" on a collapsed user message renders as a narrow column with per-letter wrapping, overlapping the text

### What happened

In the Claude Code **VS Code extension** chat, after collapsing a long **user** message with **"Show less"**, the **"Show more"** control is rendered broken:

- The button is only visible on hover over the collapsed message.
- It is squeezed into a narrow column (~40px wide): the label wraps letter-by-letter (`Sho` / `w` / `mor` / `e`).
- It is positioned over the faded text in the top-left corner of the message block, instead of below it.

Clicking the broken button does expand the message again, and "Show less" then renders normally. So only the collapsed-state "Show more" is affected.


Left: expanded message with normal "Show less". Middle: collapsed message (no control visible). Right: hovering the collapsed message shows the squeezed "Show more".

### Steps to reproduce

1. Send a user message long enough to be truncated (here: a message with a fenced code block in Cyrillic, ~15 lines).
2. Expand it with "Show more", then click **Show less**.
3. Hover the collapsed message.

### Expected

"Show more" renders as a normal full-width button below the collapsed text, like "Show less" does.

### Actual

"Show more" is a narrow vertical column with per-letter wrapping, overlapping the message text, visible only on hover.

### Environment

- Claude Code VS Code extension: `anthropic.claude-code` v2.1.270 (darwin-arm64)
- VS Code: 1.137.0 (commit 645f29cc3176500b4b5762ba887cf2a7f0ffdf2c, 2026-09-08)
- Electron: 42.10.0 · Chromium: 148.0.7778.280 · Node.js: 24.18.1
- OS: macOS (Darwin arm64 27.0.0)
- Not specific to these versions: the same behavior was reproducing on earlier versions of the extension / VS Code / macOS as well.

Related but different: #77004 (Show less off-screen), #85792 / #80672 (no collapse control at all).

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Start by reproducing the issue in the Claude Code VS Code extension chat: collapse a long user message with “Show less,” then hover it to inspect the “Show more” control. Trace the collapsed user-message UI and compare its layout with the expanded state; done means “Show more” is a normal full-width control below the faded text and expands the message correctly.

Written by the indexing model from the issue text.