chore(agent-development): replace emoji with text in warning callout (#37)

## Summary
Replace ⚠️ emoji with "Important -" text prefix in the agent-development
SKILL.md warning callout to comply with project style guidelines.

## Problem
Fixes #32

The SKILL.md used an emoji (⚠️) in a warning callout, which conflicts
with the project's style guideline to avoid emojis unless explicitly
requested.

## Solution
Changed `**⚠️ Field Name Difference:**` to `**Important - Field Name
Difference:**` which:
- Preserves the warning context and visibility
- Maintains the descriptive "Field Name Difference" phrase
- Complies with style guidelines

### Alternatives Considered
- `**Warning:**` with reworded text - less descriptive, loses "Field
Name Difference" phrase

## Changes
- `plugins/plugin-dev/skills/agent-development/SKILL.md`: Replace emoji
with text in line 19

## Testing
- [x] Markdownlint passes
- [x] Warning callout meaning preserved

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

Co-authored-by: Claude <noreply@anthropic.com>

Author: sjnims

plugins/plugin-dev/skills/agent-development/SKILL.md

@@ -16,7 +16,7 @@ Agents are autonomous subprocesses that handle complex, multi-step tasks indepen
 - System prompt defines agent behavior
 - Model and color customization
 
-> **⚠️ Field Name Difference:** Agents use `tools` to restrict tool access. Skills use `allowed-tools` for the same purpose. Don't confuse these when switching between component types.
+> **Important - Field Name Difference:** Agents use `tools` to restrict tool access. Skills use `allowed-tools` for the same purpose. Don't confuse these when switching between component types.
 
 ## Quick Start