argument-hint frontmatter in skills not displayed in slash command hint area

Bug Summary

When typing /<skill-name> (with trailing space) in Claude Code TUI, the slash command hint area shows only ... (ellipsis) instead of the argument-hint value defined in the skill's SKILL.md frontmatter.

Steps to reproduce

1. Create a user-level skill at ~/.claude/skills/staged-plan/SKILL.md with frontmatter:

``yaml
---
name: staged-plan
description: 建立、推進、歸檔 multi-stage feature 計畫(...)。
argument-hint: new-plan <name> | new-stage [N] | start-stage [N] | end-stage | update-plan | update-stage [N] | archive 例:/staged-plan、/staged-plan new-plan user-auth、/staged-plan start-stage 2
allowed-tools: Bash, Read, Write, Edit, Glob, AskUserQuestion
---
``

1. Open Claude Code in any project.
2. Type \/staged-plan \ (with trailing space) at the prompt.
3. Observe the hint area below the prompt.

Expected

Hint area shows (or at least starts with):

\\\
new-plan <name> | new-stage [N] | start-stage [N] | ...
\\\

Actual

<img width="366" height="114" alt="Image" src="https://github.com/user-attachments/assets/13da4cad-22a1-46da-b683-9c0a8cb7938b" />

Possible causes (speculation)

• The argument-hint string is long (~150 chars including a trailing Chinese description after the pipe-separated options)
• Contains \|\ pipe characters that may interact with YAML / parser
• Mixed ASCII + CJK characters that may affect width calculation / truncation

Other skills without \argument-hint\ in frontmatter are unaffected (no hint shown, which is expected).

System info

• Claude Code: 2.1.150
• OS: Darwin 25.5.0 (macOS, arm64 / Apple Silicon)
• Shell: zsh 5.9 (arm64-apple-darwin25.0)