Add configurable description truncation in /plugin and / (skills) menus

Problem

The /plugin browser and / (skills) menu truncate descriptions with ... when they exceed a fixed width, making it difficult to understand what plugins/skills do without opening the detail view.

Current Behavior

• Plugin descriptions are truncated mid-sentence in the /plugin UI (e.g., "Create distinctive, production-grade frontend interfaces ..." instead of the full description)
• Skill descriptions are truncated based on terminal width in the / menu output
• No way to configure truncation length or enable word-wrap
• Users must press Enter on each item to see the full description

Expected Behavior

Users should be able to:

1. Enable word-wrap for descriptions (wrap long lines instead of truncating)
2. Configure truncation length (e.g., full description, 100 chars, 200 chars)
3. See descriptions without opening the detail view

Suggested Solutions

Option A: Configurable truncation in settings.json

{
  "plugins.descriptionLength": "full" | "medium" | "short",
  "plugins.wordWrap": true
}

Option B: Terminal-width aware truncation

• For the / menu: respect terminal width and wrap instead of truncating
• For /plugin UI: increase max description width or allow multi-line descriptions

Option C: Both truncation AND detail

• Show truncated description with truncation indicator
• Pressing Space or D expands to full description in-place

Screenshots

• Latest screenshot showing /plugin UI with truncated descriptions
• Terminal screenshot showing / menu with single-line cutoff

Environment

• WSL2 terminal (Ubuntu)
• Claude Code latest
• Terminal width: ~140 columns (still truncates in both menus)

Impact

This is a quality-of-life issue for discovering plugins/skills — users often need to understand what a tool does before invoking it, and truncated descriptions make discovery harder.