Feature request: Visual customization for custom skills (icon, color, emoji, badge)

Feature Request

Summary

Allow custom skills (SKILL.md) to define visual identity through optional frontmatter fields like icon, color, emoji, or badge.

Motivation

When a project has many custom skills (we have 7: /spec, /requirement, /design, /implement, /research, /dryrun-design, /dryrun-code), the / menu becomes a wall of text. Visual cues would help users quickly identify and distinguish skills at a glance — especially in projects with a structured workflow where skills represent distinct lifecycle phases.

Proposed Frontmatter Fields

Any or all of these would be valuable:

---
name: implement
description: Implement a spec with task planning and tests
icon: hammer          # Named icon from a standard set
emoji: 🔨            # Unicode emoji prefix
color: "#4CAF50"     # Accent color in the menu
badge: "impl"        # Short badge/tag shown alongside the name
---

Use Cases

• Lifecycle workflows: Color-code skills by phase (blue for planning, green for building, orange for review)
• Skill categories: Distinguish research skills from build skills from review skills visually
• Quick scanning: An emoji prefix (🔍 /research, 🔨 /implement, ✅ /dryrun-code) makes the menu scannable instantly

Current Behavior

Skills appear as plain text entries in the / autocomplete menu with only name and description. No visual differentiation is possible.

Expected Behavior

Skills could optionally display a visual indicator (emoji, icon, color, or badge) in the / menu and anywhere else the skill name appears in the CLI output.