docs(agents): update project planning catalog count

[huahuajhu]

Summary

• update the Project Planning catalog count from 10 to 9 agents
• remove architecture diagrams from the agent list and point readers to the portable architecture-diagrams skill

Fixes #2083

Validation

• npx markdownlint-cli2 docs/agents/README.md
• npx cspell docs/agents/README.md
• npx markdown-table-formatter docs/agents/README.md

[Copilot]

Pull request overview

Updates the Agent Systems Catalog documentation to reflect the current Project Planning group composition after the architecture diagram capability moved from a dedicated agent to the reusable architecture-diagrams skill.

Changes:

• Update the Project Planning catalog count from 10 to 9.
• Revise the Project Planning description to remove “architecture diagrams” from the agent list and point readers to the portable architecture-diagrams skill documentation.

[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated 3 comments.

[Copilot]

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated no new comments.

[codecov-commenter]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 80.59%. Comparing base (d44ad1e) to head (ea03add).
⚠️ Report is 29 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #2096      +/-   ##
==========================================
+ Coverage   80.52%   80.59%   +0.06%     
==========================================
  Files         128      118      -10     
  Lines       19274    19198      -76     
  Branches       12        0      -12     
==========================================
- Hits        15521    15473      -48     
+ Misses       3750     3725      -25     
+ Partials        3        0       -3     

Flag	Coverage Δ
docusaurus	?
pester	84.23% <ø> (-0.02%)	⬇️

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see 11 files with indirect coverage changes

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[jkim323]

Closing out this PR as this issue is taken care of by this PR