Update Moody's skills and add missing cover assets

[moustafa-openai]

Summary

• Applies Moody's latest incremental skill updates across Earnings Brief, Peer Analysis, Rating Analysis, Sector Brief, and shared citation/template guidance.
• Adds the three earnings-brief cover images that were omitted from the original patch; their Git blob hashes match the original expected binaries exactly.
• Changes Rating Analysis from a PowerPoint deliverable to an HTML report and removes the old PPTX builder/dependency, as requested by the replacement patch.
• Cleans trailing whitespace introduced by the supplied patch.

Why

This follows up on #365 with Moody's latest patch and the missing binary assets they supplied separately.

Validation

• Patch applied cleanly against the latest origin/main.
• git diff --check passes.
• Plugin manifest and Rating Analysis eval JSON parse successfully with jq.
• Updated agent YAML files parse successfully.
• Static plugin-eval completed: 4/100, with the reported failures limited to existing/partner-supplied skill size and token-budget concerns.

Blocking follow-up

This remains a draft because the replacement patch repeatedly requires plugins/moody-s/skills/moody-s-rating-analysis/scripts/build_html.py, but that file was not included in the patch, the four email attachments, the repository, or prior history. Rating Analysis cannot produce its new HTML deliverable until Moody's supplies that builder. The previously missing Moody_Corp_Template.pptx is no longer required by this version.