feat(agent-development): strengthen trigger phrases in skill description

[sjnims]

Summary

The agent-development skill's description could benefit from additional trigger phrases to improve discoverability when users ask comparative or conceptual questions.

Current State

The description includes 11+ trigger phrases but misses some common user queries.

Proposed Changes

Add the following trigger phrases to the description field in plugins/plugin-dev/skills/agent-development/SKILL.md:

• "difference between agent and skill"
• "agent vs command"
• "when should I use an agent"
• "agent schema"

Rationale

These phrases represent common user questions when learning about plugin development. The skill already has an excellent comparison table (agents vs commands vs skills) that answers these questions, but users won't discover it without matching triggers.

Acceptance Criteria

• Description field includes new trigger phrases
• Description remains under 1024 character limit
• Skill triggers on test queries like "what's the difference between an agent and a skill?"

Related

• Identified during comprehensive skill review against Claude Code plugin best practices

[sjnims]

PR submitted: #20