docs: add AWS Q Developer to list of agents

[david-fraley]

Summary

• Added AWS Q Developer to the list of coding agents in the documentation
• Included link to the AWS Q Developer module on the Coder registry
• Created a new "Types of Coding Agents" section to organize the agent list

Related Issue

Closes #18113

Test Plan

Documentation change only - reviewed for accuracy and formatting.

🤖 Generated with Claude Code

Co-Authored-By: Claude noreply@anthropic.com

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