fix: remove reference to non-existent test-agent-trigger.sh script

[sjnims]

Summary

The agent-development skill references a script that doesn't exist in the scripts/ directory.

Location

plugins/plugin-dev/skills/agent-development/SKILL.md line ~188:

### Utility Scripts

Development tools in `scripts/`:

- **`validate-agent.sh`** - Validate agent file structure
- **`test-agent-trigger.sh`** - Test if agent triggers correctly  <!-- THIS FILE DOESN'T EXIST -->

Current State

The scripts/ directory only contains:

• validate-agent.sh

Impact

• Users following the documentation will encounter a missing file
• Breaks documentation accuracy and trust

Proposed Fix

Option A (Recommended): Remove the reference to test-agent-trigger.sh

Option B: Create the missing test-agent-trigger.sh script with functionality to test agent triggering

Acceptance Criteria

• No references to non-existent files in SKILL.md
• All referenced scripts exist and are functional

[sjnims]

PR submitted: #13