Add color annotations to agent definitions

[ChrisJBurns]

Summary

Adds visual differentiation to Claude Code agent definitions by assigning colors to key agents. This makes it easier to distinguish between different agent types when they appear in the UI.

• code-reviewer: yellow
• golang-code-writer: blue
• kubernetes-expert: blue
• toolhive-expert: green

Type of change

• Other (config/tooling change)

Test plan

• Verified agent frontmatter syntax is valid
• Confirmed no other changes are included

🤖 Generated with Claude Code

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 69.09%. Comparing base (caa31f5) to head (34cb297).
⚠️ Report is 1 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #4853   +/-   ##
=======================================
  Coverage   69.09%   69.09%           
=======================================
  Files         530      530           
  Lines       55127    55127           
=======================================
+ Hits        38088    38091    +3     
+ Misses      14111    14107    -4     
- Partials     2928     2929    +1     

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